Article

Feeding Ecology of Great Tits (Parus major) and Blue Tits (Parus caeruleus), Breeding in Suburban Gardens

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Abstract

Birds breeding in gardens fed their nestlings at a similar rate, and with similar sized prey, to birds breeding in woodland. There was no difference in type of prey brought by males and females in either species, but great tits brought more spiders (Araneae) and Diptera, blue tits more aphids (Hemiptera). Both species brought c15% of the nestlings' food from bird tables. There was no relationship between amount of artificial food in the diet, and nestling survival, in either species. In blue tits proportionately more spiders were fed to young nestlings (3-9 days), whilst older nestlings (14-15 days) received more artificial food and aphids. Young great tit nestlings (3-9 days) were fed greater than expected numbers of spiders, earwigs (Dermaptera) and Diptera. Blue tits brought fewer Lepidopteran larvae than expected from 07.00-16.00 h, and more aphids. Great tits brought more spiders than expected from 08.00-13.00 h, and more Diptera from 05.00-08.00 h. Both species showed a tendency to bring prey in runs. -from Authors

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... However, it has been observed that 'suboptimal habitats' have a relatively low proportion of caterpillars. This is the case of coniferous forests (Gibb & Betts, 1963;van Balen, 1973), suburban gardens (Cowie & Hinsley, 1988), orange groves (Barba & Gil-Delgado, 1990) and sclerophyllous forests (Blondel et al., 1991;Bańbura et al., 1994). Mediterranean sclerophyllous habitats are especially relevant due to their relatively high diver� sity of arthropods and the limited abundance of prey compared to deciduous forests (Blondel et al., 1991;García-Navas & Sanz, 2010). ...
... blue tits showed higher provisioning rates than great tits. Our results are in line with previous research carried out in British gardens and in a Belgium oak forest (Cowie & Hinsley, 1988;Nour et al., 1998). These differences in feeding rates could be due to the fact that blue tits have larger clutches than great tits (Cramp & Perrins, 1994). ...
... The number of visits per hour in this study was lower than the numbers found in other related studies (Cowie & Hinsley, 1988;Nour et al., 1998;García-Navas et al., 2013). That may be due to the brood size of central and northern European tit populations being larger than southern popula� tions (Cramp & Perrins, 1994). ...
Article
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Resource partitioning is a central issue in ecology because it can establish to which point similar species can coexist in the same habitat. Great tits and blue tits have been classical model species in studies of trophic competence. However, most studies on the topic have been conducted at localities where caterpillars are by far the most relevant prey brought to the nestlings. In Mediterranean mixed forests, nevertheless, the abundance of caterpillars is relatively low and it is spiders that play a key role in the diet of great tits, at least for nestlings. The aim of this paper was to study nest food provisioning to establish the degree of diet overlap of these two tit species in a Mediterranean forest. Our results showed that blue tit feeding rates were higher than those of great tits, probably to compensate for the smaller prey delivered to nestlings by blue tits. Blue tits brought more spiders than great tits, while grey tits brought larger prey and more caterpillars. This may be because larger great tits can prey upon larger prey items than blue tits. As a main result, this study supports the view of resource partitioning by great and blue tits in sclerophyllous Mediterranean forest ecosystem.
... It has previously been suggested that spiders arean essential part of the diet in Parids, and studies have recorded a high proportion of spiders in the early nestling's diet irrespective of season [e.g. 44,[45][46][47]. To identify the effects of taurine on development of behaviour, Arnold et al. [35] conducted a supplementation experiment in which taurine was added to the diet of nestling wild blue tits (Cyanistescaeruleus). ...
... The amount of dietary taurine may still be an important environmental influence on the developmental of behaviour and parental provisioning behaviour thus might have implications for the development of behavioural phenotypes. We, however, found that the amount of taurine supplied via spiders was not greater on day four after hatching than on day eight after hatching, which is not consistent with previous findings [46,50]. Moreover, the variance on day four was large and there was no consistent increase in many nests from day four to day eight. ...
... The difference in the proportion of spiders between day four and eight, and subsequently the amount of taurine chicks received via spiders at early age was not as evident as was found in other studies [46,50]. This could have multiple explanations. ...
Article
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Variation in early nutrition is known to play an important role in shaping the behavioural development of individuals. Parental prey selection may have long-lasting behavioural influences. In birds foraging on arthropods, for instance, the specific prey types, e.g. spiders and caterpillars, matter as they have different levels of taurine which may have an effect on personality development. Here we investigated how naturally occurring variation in the amounts of spiders and caterpillars, provisioned to nestlings at day 4 and 8 after hatching, is related to the response to handling stress in a wild passerine, the great tit (Parus major). Broods were cross-fostered in a split-brood design allowing us to separate maternal and genetic effects from early rearing effects. Adult provisioning behaviour was monitored on day four and day eight after hatching using video recordings. Individual nestlings were subjected to a handling stress test at an age of 14 days, which is a validated proxy for exploratory behaviour as an adult. Variation in handling stress was mainly determined by the rearing environment. We show that, contrary to our predictions, not the amount of spider biomass, but the amount of caterpillar biomass delivered per nestling significantly affected individual performance in the stress test. Chicks provisioned with lower amounts of caterpillars exhibited a stronger stress response, reflecting faster exploratory behaviour later on in life, than individuals who received larger amounts of caterpillars. These results suggest that natural variation in parental behaviour in wild birds modulates the developmental trajectories of their offspring's personality via food provisioning. Since parental provisioning behaviour might also reflect the local environmental conditions, provisioning behaviour may influence how nestlings respond to these local environmental conditions.
... In oak woods, food is more abundant, and birds' diets are more similar than in pine forest, where arthropods are less available (Massa et al. 2004). A low proportion of caterpillars in the diet is a characteristic for suboptimal habitats: pine forests (Gibb & Betts 1963, van Balen 1973, suburban gardens (Cowie & Hinsley 1988, Riddington & Gosler 1995, sclerophyllous habitats (Blondel et al. 1991) and forest fragments (Riddington & Gosler 1995). Nestling diet includes more spiders in mixed woodland (Gibb & Betts 1963). ...
... Although Great and Blue Tits nested in different types of habitat that does not necessarily mean that their diets were also different. In general, diet composition for nestlings of the two species was similar to earlier research made by other authors (van Balen 1973, Perrins 1976, Cowie & Hinsley 1988, Nour et al. 1998, Naef-Daenzer et al. 2000, Przybyło & Merilä 2000, Grieco 2002, Wilkin et al. 2009, García-Navas & Sanz 2010, García-Navas & Sanz 2011, Wiebe & Slagsvold 2014. The fact is that my research was conducted for two years in one forest complex and another year in a different location could be a weakness of this study, because variation in food availability between years could have a big effect on food collected. ...
... According to earlier works, the nestling diet of Blue Tits is 74% caterpillars (Wesołowski & Rowiński 2014), and up to 86-94% of all items (Przybyło & Merilä 2000), while for the Great Tit it is about 82% (Nour et al. 1998). On the other hand, some studies have found lower proportions of caterpillars in the nestling diet: 40% in Great Tits and 45% in Blue Tits (Cowie & Hinsley 1988). The main source of food for tits is caterpillars of three families: Geometridae, Noctuidae and Tortricidae (Betts 1955, Royama 1970, Cramp & Perrins 1993. ...
Article
Capsule: Blue Tits and Great Tits occupied different habitats within forests in Central Europe but their nestlings shared a similar diet. Aims: To quantify the differences in offspring diet and territory habitat between Great Tits Parus major and Eurasian Blue Tits Cyanistes caeruleus in two European forests, and to test whether the ecological niches of the two species overlap. Methods: Research was conducted on Great Tits and Eurasian Blue Tits, breeding in nest boxes in two forests near Kraków, Poland, during years: 2009, 2011 and 2012. Nine days after hatching, food items were collected from offspring using neck-collars. Habitat parameters surrounding each nest box were quantified. Results: Great Tit territories were in old Oak-Hornbeam forest, whereas Blue Tits often nested in mixed forest. There were no significant differences between the two bird species in the variation in their caterpillar diets for which both species were highly variable. Great Tits collected more caterpillars of Noctuidae per nest than did Blue Tits in 2009 and 2011 in Niepołomice Forest; Blue Tits collected more Tortricidae in 2011 and more spiders every year. In Krzyszkowice Forest in 2012, tits fed their nestlings in different periods and did not differ in the proportion of caterpillars. Habitat affected diet differently in each species. Conclusion: Although Great Tits and Blue Tits occupied different territories in each forest and year of research, the diets of both species’ nestlings contained similar species of invertebrates. The overlaps of the birds’ environmental needs are specific at a local scale.
... Thus, it is likely that insectivorous birds prey more vigorously on actively feeding HCLM, which induce the production of HIPVs by their host plant, rather than on paralysed HCLM. Furthermore, HCLM infesting parasitoid wasps are too small to fall into the range of prey for blue tits or great tits (Cowie and Hinsley 1988;García-Navas et al. 2012). ...
... insectivorous birds on insect parasitoids (1) for a generalist bird which reduced the number of large parasitoids (two ichneumonid wasps and one pteromalid wasp) (Battisti et al. 2000) and (2) for an unknown number of bird species and parasitoids, preying on various lepidopteran pest insects in an agricultural system (Martin et al. 2013). Blue tits and great tits are generalists and their prey is often dominated by lepidopteran larvae (Cowie and Hinsley 1988;García-Navas et al. 2012). But particularly in urban areas, both species also prey on other insects, spiders, and birdseed, if available (Cowie and Hinsley 1988). ...
... Blue tits and great tits are generalists and their prey is often dominated by lepidopteran larvae (Cowie and Hinsley 1988;García-Navas et al. 2012). But particularly in urban areas, both species also prey on other insects, spiders, and birdseed, if available (Cowie and Hinsley 1988). Foraging natural enemies of HCLM, such as the eulophid wasps Minotetrastichus frontalis and Pnigalio agraules (Jäckel et al. 2008), are very unlikely to fall prey for blue or great tits, as they are too small and alternative food sources are likely more attractive to the birds. ...
Article
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The horse chestnut leaf miner (HCLM) Cameraria ohridella Deschka and Dimic (Lepidoptera, Gracillariidae) is a novel but significant pest in Europe. Current control measures are either inefficient or environmentally harmful. Tits (Parus spp.) open the mines and prey on HCLM, but the biocontrol efficiency of this behaviour has not yet been quantified. We installed bird nesting-boxes in a biennial field study on four sites close to Brunswick (Germany). On the same sites, we counted HCLM pupae, larvae, opened and closed mines, and parasitised larvae and pupae in leaves collected from horse chestnut (Aesculus hippocastanum L., Hippocastanaceae) trees with and without bird exclusion. In both years, the HCLM number and the proportion of closed mines were higher in bird exclusion trees, particularly on sites with high abundance of tits. Hence, we suggest including the facilitation of birds, particularly tits, in future HCLM biocontrol strategies.
... Observations of poor breeding success of many bird species in urban areas have stimulated a growing interest in urban bird ecology (Chace and Walsh 2006, Rodewald et al. 2011. Several studies have highlighted smaller clutch sizes (Perrins 1965, Solonen 2001 and poorer nestling condition in cities (Cowie and Hinsley 1988, Mennechez and Clergeau 2006, Hedblom and Söderström 2012. Additionally, urbanisation effects have been found to influence avian phenology (Deviche and Davies 2014) with multiple studies having reported earlier breeding attempts in urban birds compared with rural conspecifics (Dhondt et al. 1984, Cowie and Hinsley 1987, Antonov and Atanasova 2003, Liker et al. 2008, Hedblom and Söderström 2012, Solonen and Hilden 2014, Møller et al. 2015. ...
... References: Lack 1954, Perrins 1965, Cowie and Hinsley 1988, Chace and Walsh 2006, Leston and Rodewald 2006, Isaksson and Andersson 2007, Marciniak and Nadolski 2007, Robb et al. 2008a,b, Chamberlain et al. 2009, Harrison et al. 2010, Amrhein 2014, Deviche and Davies 2014, Mackenzie et al. 2014 Acknowledgements -We thank Aimeric Teyssier, Lisa Baardsen and Sophie Philtjens for assisting in data collection, and Hans Matheve for assistance in setting up the sampling design. ...
Article
While numerous studies have reported negative effects of urbanisation on birds, few have examined the role of urban scale in influencing breeding success and many studies have relied on qualitative rather than quantitative assessments of urbanisation. This study sought to address these issues by testing the effects of urbanisation, measured at two spatial scales, on the breeding success of great tits Parus major. A nested study design, incorporating over 400 nestboxes, was used in study sites across northern Belgium with a priori quantified degrees of urbanisation at both local and regional scales. All measured breeding parameters were found to vary at one or both spatial scales of urbanisation; in more urbanised areas great tits displayed advanced laying dates but lower breeding success compared to rural areas, with smaller clutch sizes, lower nestling masses and fewer fledglings per egg. Importantly, urbanisation effects were not limited to big cities as birds breeding in gardens or parks in small towns also had comparatively low success. We found that both regional‐ and local‐scale urbanisation had consistent significant effects on laying date, clutch size and nestling mass, while the number of fledglings per egg was negatively influenced by local‐scale urbanisation only. Results of this study therefore highlight the importance of utilising multiple spatial scales in analysing urbanisation effects, as well as the potential negative impact of local urbanisation on breeding success. This calls for further investigation into mechanisms driving urbanisation effects and how these may vary at different scales. This article is protected by copyright. All rights reserved.
... In mixed Mediterranean forests, which are very heterogeneous habitats, it is possible to find a combination of individuals with generalist and specialist strategies (Pagani-N uñez et al., 2015). A breakdown of caterpillar specialization in other habitats has also been reported, such as in boreal forests (Rytk€ onen & Krams, 2003), in urban areas (Cowie & Hinsley, 1988;Solonen, 2001;Isaksson & Andersson, 2007;Whitehouse et al., 2013), agricultural areas (Redhead et al., 2013) and reforested lands (Massa et al., 2004). This great variability among individuals and populations suggests that classifying these tit species merely as caterpillar specialists may be misleading because diet specialization may vary in different habitats (Wesołowski & Fuller, 2012). ...
... Interestingly, the ways in which blue tits and great tits modify their foraging patterns in these different habitats is not consistent (e.g. T€ or€ ok, 1985, 1986Cowie & Hinsley, 1988;Solonen, 2001). At this point, we may conclude that blue tits and great tits display strong variation in the level of IDS within and between populations, which is driven by differences in habitat structure and resource availability. ...
Article
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In the last decade, an increasing body of research has addressed the extent to which different individuals within a species or population specialize in their exploitation of different food resources, which is referred to as individual diet specialization (IDS). Traditionally, researchers use the terms 'specialist' and 'general-ist', despite the inability of these labels to capture all of the complexity of IDS. In this paper, we compare the dietary specialism of great tit Parus major and blue tit Cyanistes caeruleus at different temporal and spatial scales. We use these two species to illustrate the differences within and between species in individual levels of IDS. Both of these species show greater IDS in Mediterranean habitats, where resources are less plentiful and more variable than in Northern Europe. Additionally , we also emphasize that IDS within populations may change temporally. At the same time, there are differences between species, with great tits showing a higher capacity than blue tits to specialize at both the individual and the population level. Great tits can be considered generalists at the species level and specialists at the individual level, while blue tits can be considered generalists at both the species and the individual level. Our study demonstrates that there is a need for researchers to determine the relative importance of intrinsic factors (e.g. differences between species or individuals in their behavioral flexibility or cognitive capacity) and extrinsic factors (e.g. resource base) in shaping patterns of dietary specialization. We conclude that, within and among species, different individuals respond differently to similar environmental pressures, utilize different niches and develop different functions in the ecosystem depending on their type of IDS. Therefore, we propose that label 'generalists' should distinguish between facultative generalists, which can develop new specializations, and obligate generalists, which have a limited capacity to develop novel specializations.
... In addition, cities are also characterised by a large number of human-generated food resources, such as food waste and feeders. Cowie & Hinsley (1988) emphasized the difficulty of great tits nestlings in digesting human-generated food items. ...
... able to sustain caterpillar development) are replaced by high ISA in the urban space, the more the body mass of developing great tits and blue tits is reduced: thus, high levels of ISA in the nestbox vicinity increase nestling mortality. Urbanizationdriven reductions in food availability are likely to lead to higher rates of nestling mortality related to starvation: earlier studies comparing great tit and blue tit nestlings reared in private gardens with those developing in woodlands reported how the former suffered from higher mortality rates relative to the latter (Cowie & Hinsley, 1988;Lack, 1955 (Buse & Good, 1996;zowski, Szulkin, & Sheldon, 2015), there is a higher chance that a mismatch occurs between the nestling period and the peak abundance of the most important prey items in cities (Mackenzie et al., 2014). ...
Thesis
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he number and size of cities are rapidly expanding worldwide. At present, more than 50% of the human population lives in urban settlements: a percentage expected to increase up to 70% by 2050. Many environmental variables (such as human presence, light and air pollution, builtup areas, increased temperatures) act in unison within the urban boundaries. With natural areas being replaced by man-made settlements, a variety of new selective pressures arise in urban areas. Consequently, studies inferring the impact of cities on wild organisms offer a unique insight into fitness variation within and outside of urban ecosystems. While phenotypic and environmental variation often covary as demonstrated when urban and rural populations are contrasted, evidence is limited as to whether such differences persist within the urban matrix and at a fine spatial scale. The aim of this doctoral thesis was to investigate the effects of urbanisation on the phenotypic and reproductive traits of two wild passerines: the great tit (Parus major) and the blue tit (Cyanistes caeruleus). Great tits and blue tits are two well-studied cavity breeders, able to occupy a wide range of habitats: from less disturbed natural areas, such as primary and secondary forests, to suburban villages, towns and cities. Data presented here were collected for up to 565 nestboxes distributed across several study sites within and outside Warsaw capital city borders in Poland. The setup of nestboxes was initiated in the first year of my PhD, and I was involved in the setup of all study sites that contributed to the dataset of environmental and life-history data here presented.
... Sexual conflict occurs in parental care, though, with the contribution of each sex affecting overall feeding rates of nestlings (Breitwisch et al., 1986;Davies, 1990). Provisioning rates have also been shown to vary with time of day (Cowie & Hinsley, 1988;Knapton, 1984) and age of nestlings, with provisioning decreasing as nestlings develop (but see Barba et al., 2009), because of greater demands by nestlings at an earlier age (Caffrey, 1999;Cowie & Hinsley, 1988). Nest visitation can also vary with size of food provided, with larger items expected to correlate with lower feeding rates. ...
... Sexual conflict occurs in parental care, though, with the contribution of each sex affecting overall feeding rates of nestlings (Breitwisch et al., 1986;Davies, 1990). Provisioning rates have also been shown to vary with time of day (Cowie & Hinsley, 1988;Knapton, 1984) and age of nestlings, with provisioning decreasing as nestlings develop (but see Barba et al., 2009), because of greater demands by nestlings at an earlier age (Caffrey, 1999;Cowie & Hinsley, 1988). Nest visitation can also vary with size of food provided, with larger items expected to correlate with lower feeding rates. ...
... For instance, in marsh tits, Poecile palustris, nest visit rates in the hour before fledging were not lower than in the same hour the previous day (Nilsson, 1990) and in mountain bluebirds, Sialis currucoides, parents did not perch in front of the nest with food more often on the day of fledging compared to the day before . However, in many bird species, parents do show diurnal variation in their provisioning effort and often provision disproportionally early in the day (Cowie & Hinsley, 1988;García-Navas & Sanz, 2012;Low, Eggers, Arlt, & P€ art, 2008). If parents reduce the amount of food they bring to the nest over the course of the day, the benefits of staying inside the nest will progressively decline. ...
... We found pronounced diurnal patterns in the provisioning behaviour of parents. Parents showed a peak in the number of nest visits during the mid-morning (1000e1100 local time), followed by a steady decrease over the course of the day ( Fig. 4; see also Cowie & Hinsley, 1988;Low et al., 2008;García-Navas & Sanz, 2012). As a consequence, it may be less profitable for nestlings to stay in the nest until later in the day when provisioning rates are lower. ...
Article
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In altricial birds, leaving the nest is a key life history transition associated with a high risk of mortality. Studies of numerous species have shown that young typically fledge early in the day, and it is often asserted that early fledging is important for survival; however, evidence for this hypothesis is limited. We used an automated monitoring system to obtain precise fledging times of 1582 young blue tits, Cyanistes caeruleus, from 230 nests. As expected, nestlings primarily fledged early in the day (84% fledged before midday). However, we found no evidence that early fledging was associated with higher postfledging survival (i.e. recorded the following autumn or later). We propose two alternative explanations for the morning peak in fledging. Hypothesis 1 is that some offspring reach a developmental threshold for fledging overnight and leave the nest early the next day. This is supported by our observation that offspring that fledged early in the day tended to be more developed than those that fledged later in the day, that is, they were older and had a high body mass (measured at 14 days of age) for their fledging age. Hypothesis 2 is that the timing of fledging is related to parental provisioning behaviour. Our results do not support this hypothesis. Parents reduced their nest visit rate over the course of the day, but offspring did not fledge earlier when their parents decreased their visit rate more strongly with time of day. In conclusion, our results do not support the notion that the time of fledging affects survival but suggest a link with nestling development.
... While some studies have investigated movements in cities [66,67], there remains a need for studies investigating the foraging behaviours and habitat choices of birds within the urban setting. The choice of natural versus anthropogenic food can have serious implications for avian health, as waste-supplemented diets have been shown to be nutritionally inadequate for normal chick development [68][69][70]. Ibis are known to forage on both anthropogenic and natural foods in urban landscapes, but the mechanism which drive these foraging decisions is currently unknown. ...
... Overabundance of food and lack of predators or disease has allowed urban bird populations to increase; this has been shown to decrease individual body condition and life span [29]. Further, urban avifauna may have a trade-off between offspring body condition and clutch size [29] as waste-supplemented diets have been found to be nutritionally inadequate for normal chick development [68][69][70]. Despite the rise in population within urban areas [61], it is unclear whether ibis are suffering from problems associated with urban diets. ...
Article
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Foraging decisions tend to drive individuals toward maximising energetic gains within a patchy environment. This study aims to determine the extent to which rainfall, and associated changes in food availability, can explain foraging decisions within a patchy urbanised landscape, using the Australian white ibis as a model species. Ibis density, food consumption rates and food abundance (both natural and anthropogenic) were recorded during dry and wet weather within urban parks in Sydney, Australia. Rainfall influenced ibis density in these urban parks. Of the four parks assessed, the site with the highest level of anthropogenic food and the lowest abundance of natural food (earthworms), irrespective of weather, was observed to have three times the density of ibis. Rainfall significantly increased the rate of earthworm consumption as well as their relative availability in all sites. Overall, these density and consumption measures indicate that anthropogenic derived foods, mainly from direct feeding by people, explain the apparent distribution of ibis across urban parks. However, there was evidence of prey-switching when the availability of natural foods increased following rainfall, perhaps reflecting selection of particular nutrients.
... Approximately 38% of energy consumed per hour by suburban Florida scrub jays (Aphelocoma coerulescens) was composed of peanuts and other miscellaneous anthropogenic foods (Fleischer et al. 2003). Approximately 15% of the diet provisioned to nestlings of both great (Parus major) and blue tits (Parus caeruleus) in a suburban habitat was composed of anthropogenic foods (Cowie and Hinsley 1988). Likewise, Australian magpie (Cracticus tibicen) used only minor quantities of available anthropogenic foods both when foraging and provisioning young (O'Leary and Jones 2006). ...
Article
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There is growing interest in the question of how urbanization affects the ecology of birds, across timescales from relatively short‐term physiological responses to long‐term evolutionary adaptation. The ability to gain the required nutrients in urban habitats is a key trait of successful urban birds. Foraging behavior, in itself, increasingly is recognized as a complex nutritional phenomenon, where the ratios, proportions, and amounts of macronutrients (protein, carbohydrate, and lipid) in foods, meals, and diets have been shown to exert a driving influence. Yet, despite the rising trend of urbanization, the importance of food quality and quantity in urban ecology, and the growing evidence demonstrating the pervasive and sometimes complex role of macronutrients in foraging behavior, the nutritional ecology of urban birds remains poorly understood. Here, we review the foraging behavior and role of macronutrients in the ecology of urban birds and demonstrate how incorporating a multidimensional approach to nutrition can provide new insights into their urban ecology. To that end, we demonstrate how a macronutrient‐based view can aid in understanding the relationships between natural, anthropogenic, and supplementary foods. We then provide an overview of multidimensional nutritional niche concepts that can be used to generate explanatory and predictive models for urban bird ecology. We conclude that multidimensional nutritional ecology provides an appropriate framework for understanding the roles that nutrition plays in the relationships between urban birds and their environments.
... Blue tits, however, have been shown to feed their nestlings with smaller food items (e.g. aphids (Homoptera)), while the great tit favours proportionally more spiders (Araneae), Diptera, and Lepidopteran larvae (Cowie & Hinsley, 1988, Cramp & Perrins, 1993, Eeva et al., 2005b, Eeva et al., 1997. Blue tits are also smaller than great tits (Cramp & Perrins, 1993), with the ensuing higher metabolic rate per mass unit (Svensson et al., 1998, Nilsson & Raberg, 2001; together with rapid feeding rates, this may affect metal accumulation (Eeva et al., 2009a, Root, 1990. ...
... The high nutritional value of spiders, due to high taurine and protein content (55-60%; Ramsay & Houston 2003), may explain the positive relationship between fledgling condition and total number of spiders in the nestling diet. Previous studies also highlight the important role of spiders as a key resource during chick development (Tinbergen 1960, Cowie & Hinsley 1988, Woodburn 1997, including the proper development of feathers (Gosler 1993), the visual system and the cognitive function of nestlings (Ramsay & Houston 2003, Arnold et al. 2007). Spiders constitute a greater proportion of tit nestling diet in Mediterranean forests (Pagani-Núñez et al. 2011) than those described here, which may reflect the general lack of food and harsher conditions of these ecosystems (Royama 1970, Blondel et al. 1991. ...
Article
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Capsule: The nestling diet of Blue Tits Cyanistes caeruleus is influenced by parental effort and habitat type, and consequently has an impact on breeding success. Aims: In a three-year study, we compared the nestling diet of Blue Tits in two Mediterranean forests (pinewood and oakwood) and tested its implications for breeding success. Methods: Adults were captured at the nest to obtain morphological measurements, and provisioning behaviour was recorded when chicks were 11 days old. Nestling tarsus length and body mass were measured on day 13 after hatching. Results: Caterpillars constituted the largest proportion of nestling diet in both habitats, however, higher numbers and biomass of noctuid, as well as higher numbers of tortricid larvae, were provided to nestlings in the pinewood. Furthermore, females provided tortricids more often than males, whereas males supplied more geometrid larvae and spiders. We found a more generalist diet for nestlings raised in the pinewood. Also, a greater number of young fledged when their diet included more tortricids and was more generalist, and Blue Tit nestlings raised on a diet with a higher number of spiders were in better body condition. Conclusion: Differences in nestling diet between habitat types contribute to explain variance in breeding performance and therefore demonstrate diverse foraging behaviour strategies among populations.
... Insectivorous birds are predators of lepidopteran moths, eggs and caterpillars, such as the O. brumata [61,84]. Thus, they may not only decrease the number of moth adults during the winter, but also caterpillar numbers during the spring. ...
Article
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Chemical cues play a fundamental role in mate attraction and mate choice. Lepidopteran females, such as the winter moth (Operophtera brumata), emit pheromones to attract males in the reproductive period. However, these chemical cues could also be eavesdropped by predators. To our knowledge, no studies have examined whether birds can detect pheromones of their prey. O. brumata adults are part of the winter diet of some insectivorous tit species, such as the great tit (Parus major) and blue tit (Cyanistes caeruleus). We performed a field experiment aimed to disentangle whether insectivorous birds can exploit the pheromones emitted by their prey for prey location. We placed artificial larvae and a dispenser on branches of Pyrenean oak trees (Quercus pyrenaica). In half of the trees we placed an O. brumata pheromone dispenser and in the other half we placed a control dispenser. We measured the predation rate of birds on artificial larvae. Our results show that more trees had larvae with signs of avian predation when they contained an O. brumata pheromone than when they contained a control dispenser. Furthermore, the proportion of artificial larvae with signs of avian predation was greater in trees that contained the pheromone than in control trees. Our results indicate that insectivorous birds can exploit the pheromones emitted by moth females to attract males, as a method of prey detection. These results highlight the potential use of insectivorous birds in the biological control of insect pests.
... Urban ibis mostly occupy parks which support foraging, roosting and breeding, island breeding colonies with minimal foraging resources where ibis breed and roost, and landfills which are a major foraging resource at which they seldom roost and very rarely breed (Shaw 1999;Martin et al. 2010). The choice of natural versus anthropogenic food has serious implications for the heath of avian communities in the future, with wastesupplemented diets having been shown to be nutritionally inadequate for normal chick development (Cowie and Hinsley 1988;Smith and Carlile 1993;Pierotti and Annett 2001). During rainfall events, the availability of anthropogenic food may decline in parklands as people avoid the outdoors, triggering a change in foraging behaviour. ...
Article
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Using a seven-year data set of visitation of an inner city park by the Australian white ibis, we investigated whether rain events were correlated with ibis abundance in the park. The park is associated with high levels of anthropogenic food, but relatively low levels of natural food sources. For all magnitudes of rainfall tested, ibis abundance significantly decreased after a rainfall event, although stronger responses were associated with higher rainfall, with a 46% decline in ibis abundance following rainfall events of ≥60 mm. Average ibis abundance was higher during the dry, non-breeding period than during the breeding period, and variation associated with rainfall was particularly pronounced in the non-breeding period. However, the rainfall response was still evident in both periods. Results suggest that rainfall influences the ibis distribution in urban centres either by decreasing anthropogenic food supplied to the birds, forcing the birds to relocate to forage, or increasing the amount of natural food available elsewhere, or a combination of the two. Increased rainfall intensified the response by ibis, and our results demonstrate the importance of climatic processes on the behaviour of urban birds.
... The timing of the breeding season would have evolved through raising the nestlings at the time when their food requirements coincide with the period of maximum food supply. P major is mainly insectivorous ali through the breeding period (Betts, 1955 ;Gibb & Betts, 1963 ;Royama, 1970 ;van Balen, 1973 ;Minot, 1981 ;Cowie & Hinsley, 1988 ;Barbara & Gii-Delgado, 1990 ;Barba et al., 1994 ). The insects cycle is known to be closely synchronized with the phenology of the plants on which the insects depend directly or indirect) y (Jordana et al., 1990 ;Rodriguez et al. , 1 994). ...
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This study compares breeding patterns of nestbox-breeding Great Tits (Parus major) between two adjacent forest habitats: a pine plantation and a Mediterranean holm oak Quercus rotundifolia forest. Breeding density increased in both forests when nestbox density was raised. The breeding season started earlier in the pinewood, but tended to end at the same time in both habitats. Reproductive effort was higher in the plantation as reflected in egg volume rather than clutch size. Time of season had an effect on clutch size but not on the size of the eggs which remained constant throughout the breeding season. Breeding success was associated with habitat, with both the number of fledglings and their weight being higher in the pinewood. These parameters showed a seasonal trend in the pinewood but not in the holm oak forest. Our results show that Great Tit achieves a higher reproductive performance in the pinewood in spite of its recent settling in this habitat.
... For example, orthoptera and coleoptera contain almost twice the level of chitin as arachnida or lepidoptera (Kaspari 1991;Magrath et al. 2004); so, arachnida and lepidoptera represent a high-quality food. Other studies focussing on the diet of altricial nestlings have also concluded that arachnida and lepidoptera are among the most preferred prey items because of their relatively low chitin content (Cowie and Hinsley 1988;Grundel and Dahlsten 1991), but also because of their high content of Significance codes: *p < 0.05, **p < 0.01, ***p < 0.001 certain amino acids (Ramsay and Houston 2003). Consequently, the higher quantity of arachnida and lepidoptera provided to BSR biased toward males is likely to be both energetically and nutritionally superior. ...
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In birds, the frequency with which the parents feed the young can vary considerably. Because of sexual differences in the begging behaviour and/or differences in the food requirements of the nestlings, brood sex ratio (BSR) is an important factor that may influence parental provisioning behaviour. Disparities in the quantity and quality of prey received by the sexes have been reported in a range of sexually size-dimorphic birds. However, to our knowledge, no study has evaluated prey composition delivery to nestlings in relation to BSR in a non-dimorphic size bird species. Because BSR influences provisioning rate in dimorphic and non-size dimorphic species and because in dimorphic species, BSR influences prey composition delivered to the nest, we hypothesised that similar to dimorphic species, BSR may influence prey composition delivered to nestlings in non-size dimorphic species. We quantify parental provisioning rate and prey composition of prey delivered to nestlings in relation to BSR in the Thorn-tailed Rayadito (Aphrastura spinicauda) a non-dimorphic and altricial passerine bird. At the population level, we found that Thorn-tailed Rayadito mothers delivered more insect larvae to the nest when compared to the father, who provided the brood with a diet more diverse in composition. However, when we considered BSR, mothers delivered a greater quantity of arachnida and lepidoptera items (high-quality foods) in male-biased BSR. In addition, nestling weight gain increased in line with the proportion of high-quality food in the diet. Our results suggest that when considering non-dimorphic species, there may be more subtle, but nevertheless important, differences, in explaining parental care behaviour in species with bi-parental care. Significance statement In birds, the frequency with which the parents feed the young can vary considerably. Because of sexual differences in the begging behaviour and/or differences in the food requirements of the nestlings, brood sex ratio is an important factor that may influence parental provisioning behaviour in sexual size species. For the first time, we evaluated prey composition delivery to nestlings in relation to BSR in a non-size dimorphic bird species. We found that the mother of the Thorn-tailed Rayadito delivered a greater quantity of lepidoptera and arachnida (high-quality food) items in a male-biased brood. In addition, nestling weight gain increased with the proportion of high-quality food in the diet. Our results suggest that in non-dimorphic species, there may be more subtle, but nevertheless important, differences in explaining parental care behaviour in species with bi-parental care.
... Gaining enough energy each day to ensure overnight survival is particularly important for small passerines: individuals in the tit family (Paridae) can lose up to 10% of their body weight overnight in winter [13]. Supplementary feeding may off-set the effects of winter resource depletion [14] and in many cases a winter feeding station may be the most abundant and dependable food source in a particular area [15]. Supplementary feeding has been recorded as having a number of other benefits to birds, including larger clutch sizes (house sparrows Passer domesticus [16]), better body condition and more rapid recovery from injury (Carolina chickadee Parus carolinensis, tufted titmice Parus bicolor and white-breasted nuthatch Sitta carolinensis [17]). ...
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Supplementary feeding of garden birds generally has benefits for both bird populations and human wellbeing. Birds have excellent colour vision, and show preferences for food items of particular colours, but research into colour preferences associated with artificial feeders is limited to hummingbirds. Here, we investigated the colour preferences of common UK garden birds foraging at seed-dispensing artificial feeders containing identical food. We presented birds simultaneously with an array of eight differently coloured feeders, and recorded the number of visits made to each colour over 370 30-minute observation periods in the winter of 2014/15. In addition, we surveyed visitors to a garden centre and science festival to determine the colour preferences of likely purchasers of seed feeders. Our results suggest that silver and green feeders were visited by higher numbers of individuals of several common garden bird species, while red and yellow feeders received fewer visits. In contrast, people preferred red, yellow, blue and green feeders. We suggest that green feeders may be simultaneously marketable and attractive to foraging birds.
... Even those species that are able to adapt to urban environments show striking differences from populations in natural habitats in many aspects of their ecology (e.g. Cowie and Hinsley 1988;Horak 1993;Chace and Walsh 2006;Chamberlain et al. 2009). Generalist species are better able to exploit urban environments (e.g. ...
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Impacts of urbanization on biodiversity are commonly studied using urbanization gradients which provide a space-for-time substitution in estimating consequences of urban expansion. Rates of urbanization and human population growth are high in tropical countries of the developing world, which also hold most of the world’s biodiversity hot-spots, yet few studies have considered biodiversity trends along urban gradients in these regions. Bird communities across a gradient of nine sites in Uganda, from the city centre of Kampala to outlying rural locations, were studied over a six year period. These sites were ordered along an urbanization gradient using Principle Components Analysis based on habitat variables estimated at each site. Bird species richness showed a decrease from rural to urban sites, a trend especially evident in forest birds. There was no clear pattern in total abundance, total biomass or biomass per individual along the gradient. However, this latter result was heavily influenced by a colony of Marabou Storks at one site. When this species was omitted, there was evidence of a positive trend with urbanization, showing that as species richness decreased, the bird community was increasingly dominated by larger species with increasing urbanization, which were mainly scavengers able to exploit human refuse. These results provide further support for the negative impacts of urbanization on species richness, but also demonstrate trends in abundance and biomass are variable across different regions. In particular, the increasing dominance of larger species in urban areas may be relevant to certain geographic and/or socioeconomic contexts.
... In total across the entire study period, 237 bread was consumed the most (104 g), followed by peanuts (79 g) and cheese (75 g). Great Tits had a particularly strong preference for peanuts, which has been observed 260 in an earlier study (Cowie and Hinsley 1988). Blue Tits showed the same preference. ...
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Capsule: Providing peanuts on bird feeders was shown to attract more individuals and more species than providing cheese or bread. Aims: To investigate how the provision of different human-derived foods affected visit rates of urban birds at bird feeders. Methods: A fully replicated study design was set up in parkland, offering a binary choice from three food types (peanuts, bread and cheese) on bird tables. Birds were observed by using a scan-sample method. Results: Peanuts attracted more visits, and a greater diversity of bird species, than cheese or bread. This preference was strongest for Blue Tits Cyanistes caeruleus and Great Tits Parus major, whereas European Robins Erithacus rubecula visited all food types equally, and Blackbirds Turdus merula preferred cheese. Bread was the most consumed food type when measured by mass, but this could be linked to varying bite sizes. Conclusion: Our results indicate that birds preferred to visit feeding stations with the most protein- and energy-rich foods, but that some birds still chose the carbohydrate-rich bread. The findings indicate that peanuts, rather than household scraps like bread and cheese, attract the highest number of species and individuals to bird tables. The findings will be of interest to the public and to organizations providing information on bird feeding for recreational purposes.
... Food availability is one component of the biotic environment that may have profound impacts on geographic variation in species occurrence and productivity. Tits are mainly insectivorous during the breeding season (Betts 1955;Cholewa & Wesołowski 2011), and whilst they have been shown to rely heavily on an ephemeral peak in caterpillar abundance (Feeny 1970;van Dongen et al. 1997;Southwood et al. 2004) for provisioning of nestlings (Visser et al. 1998;Charmantier et al. 2008), at other times during the spring adult birds prey upon a broad range of additional taxa that includes flying invertebrates such as Hemiptera, Diptera and Hymenoptera (Betts 1955;Cowie & Hinsley 1988). Woodland invertebrate diversity and abundance varies considerably between tree species (Southwood, Moran & Kennedy 1982;Kennedy & Southwood 1984). ...
Thesis
There is ample evidence that climate change is impacting on phenology and it has been suggested that this may generate trophic mismatches. A key system for investigating phenology and trophic mismatch occurs in spring in temperate deciduous woodlands, where folivorous caterpillars and their predators, insectivorous passerines, are reliant upon ephemeral resources for reproductive success and survival. However, studies are primarily conducted within single-site, oak- (Quercus sp) dominated woodland and focus on a single caterpillar species, winter moth (Operophtera brumata), despite these passerines being habitat generalists with large geographic ranges. It remains to be seen whether insights gained from these studies can be generalised on the landscape scale across different habitats. In this thesis, I explore the extent to which geographic and habitat variation operates in this system and attempt to expand the system beyond a linear single-species food chain into a more biologically realistic multi-species food web. I also identify the most important environmental factors predicting the phenology of the passerines to allow better predictions of how their phenology could alter under future climate change scenarios. To address these questions, I established a novel 220km transect of Scotland incorporating 40 field sites that vary in elevation and the type of deciduous woodland habitat, monitoring six blue tit (Cyanistes caeruleus) nestboxes, tree and invertebrate phenology and abundance, at each site throughout the springs of 2014-16. Firstly, I assess how blue tit occupancy and productivity are affected by the variation in fine-scale woodland habitat, latitude, elevation and prey availability that exists along the transect (Chapter 2). I find that habitat variables strongly affect fledging success but not occupancy or clutch size, whilst occupancy exhibits biogeographic trends, revealing that the relationship between breeding decisions and outcomes differs among habitats and implies that it may be difficult to generalise results from one habitat to others. Next, I aim to identify the environmental aspects which play a role in regulating blue tit reproductive phenology by examining the ability of temperature, tree phenology, invertebrate prey abundance and photoperiod to predict nest initiation and laying dates (Chapter 3). I find that night-time temperature in early spring is the most important predictor of both nest initiation and lay date (slopes ~ -3days/°C) and I suggest that this supports the hypothesis that temperature acts as a constraint on timing rather than a cue. Invertebrate abundance is also a positive correlate of lay date, possibly allowing fine-tuning of timing. This knowledge provides clearer foundations from which to predict future phenological change and possible trophic mismatch in this system. There is the potential that the apparent effect of temperature on blue tit reproductive phenology is indirect and mediated by diet, which is largely undescribed in the period prior to breeding. Therefore, in Chapter 4 I examine how blue tit diet varies across habitat, geography and time, and whether there is a dietary cue utilised to initiate breeding phenology, using data from metabarcoding faeces collected from nestbox-roosting adults in early spring. Geographic variation in diet is substantial, with high site-to-site dietary turnover (β-diversity), as well as high turnover along the elevational and latitudinal gradients studied. Dietary α-diversity (richness) is unaffected by geographical variables, but increases over time, with significant pre-breeding dietary increases in Lepidoptera and Hemiptera signifying a possible cue. In addition, these data provide the most comprehensive next-generation insights into the diet of a wild bird to date and identify 432 prey taxa. Finally, I analyse how biogeographic and habitat variables affect the phenology, abundance and diversity of caterpillars (Chapter 5). Host tree species’ varied significantly in their likelihood of hosting a caterpillar, with oak and willow (Salix sp.) the most likely. Biogeography had less effect on the likelihood of caterpillar occurrence, but elevation delayed peak date by 3.7 days/100m increase. There was also support for the spring caterpillar peak being dominated by a few key species, with over half of all caterpillars identified being of just three of the 62 total species, including winter moth. These findings contribute to understanding how the temporal distribution of caterpillars varies across habitats on the landscape scale. Taken together, the findings of this thesis reveal considerable geographic and habitat variation throughout this system, in both the composition of the food web and the impacts on blue tit productivity, demonstrating why caution must be exercised when extrapolating findings from one location or habitat to others.
... It is known that the maintenance of stand structural complexity is critical for forest conservation of biodiversity (Sanesi et al. 2009;Lindenmayer et al. 2006). Old trees have been shown to be of great importance for some species and for biodiversity in general (Andersson and Östlund 2004;Cowie and Hinsley 1988). In this study, we tested whether the abundance of forest species increased with the presence of large trees (high mean DBH). ...
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A significant decline in biodiversity is associated with the current and upcoming degree of urbanization. A challenging strategy to address this conflict is to make urban growth compatible with biodiversity protection and in this context urban parks can play a crucial role. Urban systems are highly dynamic and complex human-shaped ecosystems, where the relationship between species and environment may be altered and make the preservation of biodiversity within them a challenging goal. In this study, we analysed how different environmental features affect bird biodiversity in one of the most urbanized areas of Italy (the metropolitan area of Milan) at different spatial scales. Bird surveys were conducted in fifteen urban and peri-urban parks and environmental variables at landscape and local scale recorded. Results showed that a mixture of land covers and the presence of water bodies inside urban parks favoured species occurrence and abundance at landscape scale, but a surrounding dense urban matrix deflated biodiversity. At local scale, woodland cover and presence of water bodies were key determinants in ensuring overall high biodiversity but local-specific vegetation management produced an unusual pattern for forests species. In particular, the maintenance of large trees may not result in biodiversity support for forest bird species if large trees are not located in woodland areas with a significant tree density. To understand biodiversity patterns and provide useful information for urban planning and design, we need to provide insights into species/environment relationships at multiple scales in the urban environment.
... able to sustain caterpillar development) are replaced by high ISA in the urban space, the more the body mass of developing great tits and blue tits is reduced: thus, high levels of ISA in the nestbox vicinity increase nestling mortality. Urbanizationdriven reductions in food availability are likely to lead to higher rates of nestling mortality related to starvation: earlier studies comparing great tit and blue tit nestlings reared in private gardens with those developing in woodlands reported how the former suffered from higher mortality rates relative to the latter (Cowie & Hinsley, 1988;Lack, 1955 (Buse & Good, 1996;zowski, Szulkin, & Sheldon, 2015), there is a higher chance that a mismatch occurs between the nestling period and the peak abundance of the most important prey items in cities (Mackenzie et al., 2014). ...
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Introduction Rapid environmental change driven by urbanisation offers a unique insight into the adaptive potential of urban‐dwelling organisms. Urban‐driven phenotypic differentiation is increasingly often demonstrated, but the impact of urbanisation (here modelled as the percentage of impervious surface (ISA) around each nestbox) on offspring developmental rates and subsequent survival remains poorly understood. Furthermore, the role of selection on urban‐driven phenotypical divergence was rarely investigated to date. Methods and Results Data on nestling development and body mass were analysed in a gradient of urbanisation set in Warsaw, Poland, in two passerine species: great tits (Parus major ) and blue tits (Cyanistes caeruleus ). Increasing levels of impervious surface area (ISA) delayed the age of fastest growth in blue tits. Also, nestling body mass was negatively affected by increasing ISA 5 and 10 days after hatching in great tits, and 10 and 15 days in blue tits, respectively. High levels of ISA also increased nestling mortality 5 and 10 days after hatching in both species. An analysis of selection differentials performed for two levels of urbanisation (low and high ISA) revealed a positive association between mass at day 2 and survival at fledging. Discussion This study confirms the considerable negative impact of imperviousness –a proxy for urbanisation level‐ on offspring development, body mass and survival, and highlights increased selection on avian mass at hatching in a high ISA environment.
... To test the deflection hypothesis and other 2 alternative hypotheses, we conducted visual modeling to determine whether domestic chicks and blue tits (Cyanistes caeruleus Linnaeus, 1758) could distinguish the color of A. minuta spiders from that of the silk decorations against a background of the natural habitat. Although the blue tits were not used in predation experiments in this study, we tested them in this feature as many passerine birds such as great tits and black tits are common predators of arthropods in the field (Cowie & Hinsley 1988). In addition, the visual system of blue tits, but not other passerine birds, has been well studied, and it is a good representative of the UV-sensitive visual system in passerine birds (Gomez et al. 2014;Olsson et al. 2015). ...
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Although camouflage as an effective antipredator defence strategy is widespread across animals, highly conspicuous color patterning is not uncommon either. Many orb-web spiders adorn their webs with extra, bright white silk. These conspicuous decorations are hypothesized to deter predators by warning the presence of sticky webs, camouflaging spiders, acting as a decoy, or intimidating predators by their apparent size. The decorations may also deflect predator attacks from spiders. However, empirical evidence for this deflection function remains limited. Here we tested this hypothesis using the X-shaped silk cruciform decorations built by females of Argiope minuta. We employed visual modelling to quantify the conspicuousness of spiders and decorations from a perspective of avian predators. Then we determined actual predation risk on spiders using naïve chicks as predators. Spider bodies and decorations were conspicuous against natural backgrounds to the avian visual systems. Chicks attacked the spider main bodies significantly less frequently on the decorated webs than on the undecorated webs, thus reducing predation risk. When both spiders and decorations were present, chicks also attacked the spider main bodies and their legs or decorations, and not randomly: they attacked the legs or decorations sooner and more frequently than they attacked the main bodies, independence of the ratio of the surface area between the decoration and spider size. Despite the increase in detectability, incorporating a conspicuous cruciform decoration to the web effectively defends the spider by diverting the attack towards the decoration or leg, but not by camouflaging or intimidating, thus, supporting the deflection hypothesis. This article is protected by copyright. All rights reserved
... Research has mainly focused on bread and seed feeding rather than sugar water feeding, probably because bread and seed is the most common food provided for granivorous species, which are common natives in the North America and Europe (Cowie and Hinsley 1988;Orams 2002;Rollinson et al. 2003;Chace and Walsh 2006;Galbraith et al 2014). For example, householders in the USA and the UK purchase 500 000 tonnes of birdseed annually (O'Leary and Jones 2006) and mixed seed is the number one food provided by householders in Canada (Prescott et al. 2000). ...
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Feeding backyard birds with sugar water is increasingly popular in urban areas, but it has poorly understood effects on bird assemblages. In New Zealand, ca. 20% of households engaged in feeding wild birds use sugar water, often in an attempt to attract native, nectarivorous birds. Developing best practices for sugar water feeding could be a powerful tool for attracting these species in urban areas. However, it is currently unclear whether these feeders actually support native species, and, if so, which feeding practices are most effective in increasing visitation. We surveyed New Zealanders who provide sugar water to birds about their feeding practices via an online questionnaire. The aim of our research was to understand existing practices and their effect on attracting native species, as well as the motivations and social factors behind urban sugar water bird feeding. Our results show that this practice is popular throughout the country with the majority of households successful in attracting native nectarivorous species to their gardens. Sugar water feeder type had the largest effect on reported species richness at feeders in comparison to other factors (e.g. sugar concentration). Feeders specifically designed for nectarivorous birds, namely the Tui Nectar Feeder™, are more successful at attracting natives in comparison to other commonly used feeder types. Thus, individual householder decisions around feeder use can have important consequences for bird species composition in urban gardens. Future research is needed to understand the consequences of sugar water feeding for bird communities and individual bird health.
... We assumed that nestling Great Tits, with their slightly different breeding ecology and body sizes, may respond to environmental stressors in slightly different ways. In contrast to Blue Tits, Great Tits are more plastic in terms of foraging behaviour, prey diversity and habitat use (Cramp and Perrins, 1993;Cowie and Hinsley, 1988). Consequently, their blood glucose concentration may exhibit a distinct pattern. ...
Article
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The main aim of this study was to examine if blood glucose concentration displays any pattern of variation between years and distinct habitats. Bird blood glucose concentration reflects their high metabolic demands and is influenced by a variety of environmental factors. Therefore variation in glucose levels of free-living birds is an important aspect of their functional ecology. We now present results concerning variation in glucose concentration in the blood of Great Tit (Parus major) nestlings (∼ 14-day-old). We also compare the obtained results with variation in blood glucose nestlings Blue Tit (Cyanistes caeruleus) published elsewhere. Our present study was conducted in central Poland in an 8-year period, 2005–12 in two distinct habitat types: an urban parkland and a rural deciduous forest. The most important findings of the study were: (i) mean levels of blood glucose varied markedly between years; (ii) glucose concentrations were significantly higher in the parkland study area; (iii) heavier nestlings were characterised with lower blood glucose levels; (iv) there was a negative relationship between fledging success and per-brood mean glucose concentration in the urban park site but not in the forest site; and (v) Great Tit nestlings were characterised by significantly higher blood glucose levels than Blue Tits nestlings. Variation in glucose concentration of nestling Great Tits shows a consistent spatio-temporal pattern which is generally similar to that found in Blue Tits.
... However, great tits are more ground-feeding birds compared to blue tits, who feed almost exclusively arboreal in the canopy during the breeding season (Krebs, 1971;Cramp and Perrins, 1993). Consequently, blue tits feed almost solely on herbivorous prey, such as aphids and caterpillars (Cowie and Hinsley, 1988), which are expected to mostly accumulate short-chain PFAAs. These short-chain compounds are highly water soluble and are known to be dominantly present in contaminated plant tissues, especially the leaf parts (Blaine et al., 2013;Brendel et al., 2018). ...
Article
Eggs of terrestrial bird species have often been used to biomonitor both legacy and emerging anthropogenic contaminants , such as perfluoroalkyl acids (PFAAs). However, few, if any, studies have examined whether results obtained in a given model species can be generalized across bird species. Therefore, we compared potential differences in egg PFAA profile and concentrations between two widely studied passerine species, great tit (Parus major) and blue tit (Cyanistes caeruleus), which are similar in many aspects of their ecology and life history. Whole clutches of both species were collected from the same breeding season and at the same place (Antwerp, Belgium), enabling us to study laying order effects. Additionally, we evaluated how egg PFAA concentrations for both species changed along a distance gradient from a PFAA point source. Although the sum PFAA concentrations did not significantly differ between great tits and blue tits, large differences in PFAA profile and laying order effects were observed. Great tits showed a more diverse PFAA detection profile, including perfluorooctane sulfonic acid (PFOS) and various long-chain perfluorocarboxylic acids (PFCAs) but no short-chain compounds. Contrarily, short-chain PFCAs (perfluorobutanoic acid (PFBA) and perfluorohexanoic acid (PFHxA)) were only detected in blue tit eggs. The variation of perfluorooctanoic acid (PFOA) concentrations within clutches was large in both species , although laying order effects on PFOA concentrations were only found in blue tits. Although egg PFOA concentrations of both species decreased similarly from the fluorochemical point source onwards, more variation in egg PFOA concentrations could be explained by distance from the fluorochemical plant in great tits (60%) than in blue tits (15%). Results showed that both species markedly differed in terms of egg PFAA profile and concentrations , most likely reflecting differences in diet, foraging habits and egg protein composition. Finally, biomonitor-ing results of PFAAs in eggs are likely not generalizable across bird species.
... For example, the percentage of spiders in the diet and the type of spiders ingested are likely influenced by a suite of factors like spider availability, life stage, and other species-specific life-history traits that influence foraging strategy, which were not accounted for in SBAWV calculations (Gajdoš and Krištín 1997). In the present study, the data used for the percentage of a bird's overall diet that was composed of spiders were distilled to a single value for nestling chickadees, house wrens, and American robins; however, increased spider provisioning to younger-life stage nestlings has been reported with multiple bird species (Royama 1970;Pinkowski 1978;Cowie and Hinsley 1988;Arnold et al. 2007;Radford 2008;Browning et al. 2012), meaning that the SBAWVs calculated could be underprotective for younger nestlings (i.e., house wrens and red-cockaded woodpeckers). Many birds in the present study are also known to prey on adult aquatic insects (e.g., mayflies and dragonflies) and terrestrial insects (e.g., caterpillars and grasshoppers), which likely contribute additional, and unaccounted for, dietary contaminant exposure. ...
Article
There is growing concern over the health of North American birds, as evidence suggests substantial population declines. Spiders are prominent dietary items for many bird species and mediate the transfer of contaminants to arachnivorous birds that consume them. Few studies have investigated the potential risk the spider exposure pathway poses to these birds, as most studies have focused on piscivores. In this study, we developed new chronic and acute As, Cd, Cu, Pb, Ni, Se, Zn, and MeHg spider‐based avian wildlife values (SBAWV) for multiple adult and nestling birds (primarily passerines) and then used the newly generated SBAWVs to characterize the risk to birds across two study areas: (1) five reaches in the Southern Appalachian Mountains, an area with substantial mercury deposition but minimal anthropogenic impact and (2) four reaches adjacent to the Emory River, an area impacted by the largest fly coal‐ash spill in U.S. history. In this study we identified MeHg and Cu, Pb, Se, and Zn as contaminants of potential concern (COPC) at the Appalachian Mountain and Emory River study areas, respectively, based on dietary exposure of aquatic contaminants via riparian spiders. The identification of COPC at both study areas due to dietary spider exposure is notable not only because the spider exposure pathway has largely been uninvestigated at these sites, but also because the aquatic systems in both areas have been studied extensively. These results indicate that the selection of spider taxa can impact risk characterization and that the spider exposure pathway is important to consider when assessing potential risk even in areas where the, particularly for passerine birds. This article is protected by copyright. All rights reserved.
... In addition, particular prey types may be a nutritional adaptation to early offspring developmental stages. For example, many studies have found that insectivorous birds feed younger nestlings a higher proportion of spiders than older nestlings (Betts 1955;Royama 1970;Cowie & Hinsley 1988;Radford 2008), and one study showed that spider-rich diets positively affected offspring growth (Garc ıa-Navas, Ferrer & Sanz 2013). In short, offspring developmental stage may alter dietary needs, apart from constraints imposed by the availability of prey items. ...
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1.Climate change may cause phenological asynchrony between trophic levels, which can lead to mismatched reproduction in animals. Although indirect effects of mismatch on fitness are well described, direct effects on parental prey choice are not. Moreover, direct effects of prey variation on offspring condition throughout their early development are understudied. 2.Here we used camera trap data collected over two years to study the effects of trophic mismatch and nestling age on prey choice in pied flycatchers (Ficedula hypoleuca). Furthermore, we studied the effect of mismatch and variation in nestling diet on offspring condition. 3.Both experimentally induced and natural mismatch with the caterpillar peak negatively affected absolute and relative numbers of caterpillars and offspring condition (mass, tarsus and wing length), and positively affected absolute and relative numbers of flying insects in the nestling diet. Feeding more flying insects was negatively correlated with nestling day 12 mass. 4.Both descriptive and experimental data showed preferential feeding of spiders when nestlings were <7 days old. Receiving more spiders during this phase was positively correlated with tarsus growth. 5.These results highlight the need for a more inclusive framework to study phenological mismatch in nature. The general focus on only one prey type, the rarity of studies that measure environmental abundance of prey, and the lack of timing experiments in dietary studies currently hamper understanding of the actual trophic interactions that affect fitness under climate change.
... But caterpillar abundances are often observed to be higher. Cowie and Hinsley 1988;Chace and Walsh 2006;Leston and Rodewald 2006;Isaksson and Andersson 2007;Robb et al. 2008;Chamberlain et al. 2009;Mackenzie et al. 2014 Food Food Food Food quality quality quality quality ...
Thesis
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Many studies have reported negative effects of urbanisation on bird breeding success, with the role of food thought to play a particularly significant role. The negative effects of city environments on birds have lead researchers to suggest that urban areas may represent ecological traps, whereby individuals settle preferentially in urban habitats but show poor reproductive success relative to other available rural habitats. In this context, this thesis sought to test the effects of urbanisation measured at two spatial scales on both the breeding success of great tits Parus major, and its food during the breeding season. A nested design was used in study sites in northern Belgium with a priori quantified degrees of urbanisation at both local and regional scales. Results found breeding success to vary at one or both spatial scales of urbanisation for all measured parameters: in urban areas great tits displayed advanced laying dates and breeding success was lower than in rural areas, with smaller clutch sizes, lower nestling masses and fewer fledglings per egg. Results regarding food showed that the proportion of caterpillars provisioned to nestlings varied with local scale urbanisation, with significantly lower proportions of caterpillars provisioned to nestlings in urban areas. Moreover, the proportion of caterpillars provisioned was found to have a significant positive effect on nestling mass. Provisioning rates and caterpillar lengths were not found to vary with urbanisation. Results of this study suggest that food quality plays a key role in breeding success in cities, highlight the importance of utilising multiple spatial scales in analysing urbanisation effects, and ultimately provide support to the ecological trap hypothesis.
... However, studies on great (Parus major) and blue (P. caerulescens) tits (Cowie and Hinsley 1988) and on laughing gulls (Larus atricilla, in urban areas did not show a negative effect of human-provided foods on nestlings. Hence, whether or not human-provided foods are of low quality for nestlings may depend on the type of human-provided foods and species-specific nutritional needs and digestive capabilities of nestlings. ...
Article
Immer mehr Arten leben in urbanisierten Gebieten wo sie Zugang zu anthropogenem Futter haben. Man weiss, dass dieses Futter die Artenzusammensetzung verändert, die genauen Ursachen sind aber unbekannt. Beim Florida Scrub-jay (Aphelocoma coerulescens) ist der Zugang zu anthropogenem Futter mit reduziertem Wachstum und Ueberleben der Nestlinge verbunden. Das Ziel dieser Studie war, den Einfluss des anthropogenen Futterangebotes auf die Nestlingfitness zu untersuchen. Zufütterungsexperimente zeigten, dass die Nestlinge futterlimitiert sind. Diätanalysen konnten jedoch keinen Zusammenhang zwischen dem Konsum von anthropogenem Futter und dem Nestlingswachstum feststellen. Futterwahlversuche deuten darauf hin, dass die Adultvögel die schlechte Qualität des anthropogenen Futters für ihre Jungen abschätzen können und legen nahe, dass die Eltern wegen der reduzierten Menge an natürlichem Futter dazu gezwungen werden, anthropogenes Futter zu wählen. Beobachtungen während der Futtersuche zeigten jedoch, dass die urban Eltern häufiger natürliches und anthropogenes Futter finden als die Eltern im ursprünglichen Habitat. Es könnte sein, dass die Eltern anthropogenes Futters wählen, weil dessen Angebot sehr gross ist und damit zu maladaptiver Futterwahl führt. Diese Studie zeigt aber auch, dass das veränderte Futterangebot nicht die einzige Ursache für die reduzierte Nestlingsfitness sind, andere Faktoren, z.B. ein erhöhtes Prädationsrisiko im urbanen Gebiet, scheinen ebenfalls dazu beizutragen. An increasing number of species are living in urbanized areas worldwide and have access to human-provided foods. Human-provided foods are known to change urban species communities, however, the exact causes of these changes remain unknown. In the Threatened Florida Scrub-jay (Aphelocoma coerulescens) the access to human- provided foods in suburban habitats is associated with decreased nestling growth and survival compared to the wildlands. The goal of this study was to investigate whether human-provided foods in suburban habitats contribute to decreased nestling fitness. A food supplementation experiment demonstrated that nestling growth and survival is food limited, however diet analyses failed to determine any relationship between the consumption of human-provided foods and nestling growth. Food choice experiments showed that parents can assess the low quality of human-provided foods for nestlings, indicating that suburban parents may switch to human-provided foods only because the availability of natural foods is low in the suburban habitats. Foraging observations, however, showed that suburban parents feed human-provided foods to nestlings even though they find natural foods and human-provided foods more often than wildland parents do. This finding suggests that the high predictability of human-provided foods might cause maladaptive food choices. Further, the results of this study revealed that other factors, such as increased predation risk, may negatively affect suburban nestling fitness.
... In unmanipulated conditions male and female blue tits fed their offspring at a rather constant rate throughout the day, independent of nestling age. Such limited diurnal variation was also found for this species in a U.K. population 38 , which is in our study a prime condition that enables direct comparison between pre-and post-manipulated conditions during experimental days (see further). Yet, parental visit rates increased with nestling age, with almost 20% higher visit rates when nestlings were 13, relative to 7 days old. ...
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Sexual conflict over parental investment can result in suboptimal reproductive output. A recent hypothesis suggests that equality in investment, and hence conflict resolution, may be reached via coordination of parental activities like alternating nest visits. However, how robust patterns of care within couples are against temporal disturbances that create asymmetries in parental investment remains as yet to be shown. We here experimentally created such a social disturbance in a wild population of biparental blue tits (Cyanistes caeruleus) when provisioning their nestlings. We randomly caught and subsequently released one of the parents when nestlings were 6 and 12 days old respectively. On average, the parent that was caught did not resume care for nearly two hours. We then compared the levels of individual investment and within-pair coordination before, during and after the absence of the disturbed parent. We show that the remaining parent partially compensated by increasing its provisioning rate, but this compensatory response was strongest in females when nestlings were 6 days old. Once the caught parent returned to feed its nestlings, both parents resumed provisioning at a similar rate as before the disturbance. Likewise, the within-pair alternation level quickly resembled the pre-manipulated level, independent of nestling age or which sex was caught. Thus our experiment highlights the resilience of parental behaviour against temporal disturbances of individual parents.
... Les traits d'histoire de vie de la mésange bleue C. caeruleus ont été très étudiés dans la péninsule ibérique (BARBA & GIL DELGADO, 1990 ;ISENMANN et al., , 1990BANBURA et al., 1994 ;SANZ & GARCIA-NAVAS, 2008), dans le sud de la France, en Languedoc et en Corse (CRAMM, 1982 ;BLONDEL, 1985, 1991GAUBERT, 1985 ;TREMBLAY et al., 2003), au centre de l'Italie (BELLAVITA & SORACE, 1994), au niveau des îles scandinaves (PERRINS, 1979), au Gotland en Suède (PRZYBYLO et al., 2001) et en Finlande (SOLONEN, 2001COWIE & HINSLEY, 1988). En revanche, peu de travaux scientifiques ont concerné les populations nicheuses en Afrique du Nord. ...
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The reproductive phenology of the Eurasian Blue Tit Cyanistes caeruleus is influenced by many abiotic factors. Here we assess the affects of habitat type on certain parameters of breeding populations of nesting Eurasian Blue Tit in the forest of Béni-Salah. During the breeding season 2013, ninety artificial nest boxes supporting the construction of these birds' nests were installed at three different habitats in this forest: the Cork oak (Quercus suber) formation, the Algerian oak (Quercus canariensis) formation, and shrubs. Seventy-two were only occupied by nests of chickadee couples, representing an average occupancy rate of 74.44% ± 0.43. Egg laying lasted six weeks, from the beginning of April to the end of May. Two to six eggs were laid per nest box and the maximum was reached in the shrubs. Hatching and flight successes were 80.16 % and 79.67% respectively.
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Work from Master's degree, not published
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Using a food chain approach, which includes the leafing patterns of summergreen and evergreen oaks, caterpillars that feed upon them, and insectivorous tits, we examine life history variation of the birds in different habitats of the Mediterranean region. The annual renewal of leaves involves only one third of the whole foliage in the evergreen Holm oak instead of 100% in the summergreen Downy oak and occurs c. three weeks later in the former than in the latter. Caterpillars are nicely synchronized on the leafing process and are more abundant in summergreens than in evergreens. The diet of the Blue Tit includes a large diversity of prey, especially in evergreen oaks, and the way tits compensate for the low abundance of caterpillars is discussed. Blue Tits fairly match the period of food availability in summergreens on the mainland and in isolated habitats dominated by evergreens (i.e. Corsica), but they are mis-timed in evergreen habitat patches within a mainland landscape which includes both summergreen and evergreen habitat patches. We hypothesize that gene flow among sub-populations living in discrete habitat patches of different quality results in a source/sink system whereby the tits breeding in evergeen habitats must be permanently restocked by immigrants from more productive source habitats.
Article
Some models of central place foraging relate the time taken to deliver a prey to the selectivity of the forager. If birds have to travel longer, they are expected to take only larger prey. Prey selectivity may also increase if birds have more time available for search activities. I tested this last hypothesis by experimentally increasing the food available to Blue Tits during young rearing. Insect larvae were offered to breeding adults from egg hatching to fledging of the young. Provisioning rates and prey size were studied by videotaping. In experimentally overfed broods, part of the additional food was delivered to their nestlings by the adults, while the rate of feeding with natural prey decreased compared to unmanipulated pairs. Overfed males delivered larger insect larvae than control males, while females showed no response to the treatment. Overfed males could deliver larger prey at late chick ages (when presumably the chicks' demand is higher) than controls, suggesting that control males were time- (or energy) constrained. Moreover, overfed parents appeared to choose relatively more prey that may be important in the chicks' diet. The results show that prey selectivity is related to time (or energy) budgets.
Chapter
We examined shifts in the feeding habits of European Starlings along an urban-rural gradient in northwestern France by comparing the diet of nestlings in three habitats: urban, suburban and rural areas. We sampled 99 broods using the neck-collar method. Broods were adjusted to four nestlings each to exclude brood size effects on diet. We have previously shown that parents foraged within 800 m from the nest in each habitat. In all three habitats, most food items brought to nestlings were invertebrates living on and in the ground or on low vegetation. However, diet composition changed along the urbanization gradient: (1) During first nest attempts nestlings reared in the urban area received less Lepidoptera and more Coleoptera than those located in the rural area; (2) Urban and suburban nestlings received less animal food than rural nestlings and more plant food and human refuse; (3) Diet varied with nest attempt and with nestling age. We conclude that, in towns, European Starlings feeding nestlings depend heavily on grasslands despite their ability to use human refuse. We suggest that recent urban planning in France, which encourages lawn plantings, may, in part, explain the increase of urban starling populations.
Article
We present a two-patch metaecoepidemic model, in which predators, sound and infected prey occupy the first one. Both kinds of prey can migrate into a second habitat, which constitutes a refuge from the predators. Equilibria of the system and their stability properties are determined analytically and also heavily studied numerically, when too cumbersome. The results indicate that in practical situations it is necessary to carefully assess the environmental state before proceeding to any modification of it, as the consequences might be far from those foreseen.
Article
This paper investigates urban imaginaries conveyed in publications in ecology over the past century. We examine some urban ecologists’ view that urban areas have been disregarded by ecology due to negative views on cities and urbanisation. Inspired by previous work on imaginaries in social and cultural geography and political ecology, and by textual data analysis methods, we adopted a methodological framework that applies both quantitative and qualitative methods in the analysis of a corpus of 960 articles (published 1922–2018) drawn from 10 long-standing international journals in ecology. Our hypothesis is that ecology has embraced an anti-urban imaginary that is manifested in urban invisibility as well as the recurrent expression of negative ideas about cities (constituting an ‘anti-urban bias’). Our results partially confirm this hypothesis. We show that until the 1970s only a few papers were published on cities. We identify nine main themes relating to cities around which ideas about cities have been constructed (threats, pests, refuges, fragmentation, gradients, pollution, homogenisation, planetary urbanisation, and planning) and show how these ideas have been mobilised in the articles since the 1920s. We discuss the way in which these evolving ideas reflect a move from an essentially anti-urban imaginary to a more complex and ambivalent one. This shift coincides with the rise of the idea of planetary urbanisation in ecological publications, increasing recommendations regarding urban planning, and more generally, growing conceptual debates on the ecological impact of cities.
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Pitzalis M., Marangoni C., Bologna M. A., 2005. Analisi di processi di dispersione e colonizzazione tramite un GIS in tre specie di uccelli alloctoni nella fauna di Roma (Italia centrale). Alula XII (1-2): 193-205.
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Animals often show reduced reproductive success in urban compared to adjacent natural areas. The lower availability and quality of natural food in cities is suggested as one key limiting factor. However, only few studies have provided conclusive support by simultaneously assessing food availability, diet and fitness. We consolidate this evidence by taking a holistic approach, comparing blue tits breeding in forest, suburban and urban areas. We (a) assessed arthropod availability, (b) investigated parental provisioning behaviour, (c) inferred diet through stable isotope analysis, and (d) measured reproductive success. At the urban site, we found a significant reduction in caterpillar availability, the main food source of blue tits, and consequently urban tits fed their offspring with fewer caterpillars than forest and suburban birds. Stable isotope analysis confirmed that diet in the urban area was fundamentally different than in the other sites. Reproductive success was lower in both urban and suburban sites compared to the forest site, and was positively associated with volume of provisioned caterpillars. Our findings provide strong integrative evidence that urban blue tit nestlings are not receiving a suitable diet, and this may be an important limiting factor for urban populations of this and potentially many other species.
Article
The nesting behaviour of the great tit (Parus major) from nest preparation to fledging was followed continuously by video-recording in two identical nest-boxes over two seasons during 2020 and 2021 in the same large rural garden. Unexpectedly, the production of a series of regurgitation pellets (RPs) by the nestlings was recorded during the 2020 season. No pellet regurgitation was recorded during the 2021 season. Recordings were also made of adult great tits producing small RPs as they roosted. I suggest that this unprecedented RP production by nestlings resulted from the consumption of suboptimal food items due to the poor breeding season of 2020.
Article
The nesting phenology and productivity of hole‐nesting woodland passerines, such as tit species (Paridae), has been the subject of many studies and played a central role in advancing our understanding of the causes and consequences of trophic mismatch. However, as most studies have been conducted in mature, oak‐rich (Quercus sp.) woodlands, it is unknown whether insights from such studies generalise to other habitats used by woodland generalist species. Here we applied spatial mixed models to data collected over three years (2014‐2016) from 238 nestboxes across 40 sites – that vary in woodland habitat and elevation – along a 220km transect in Scotland. We evaluate the importance of habitat, biogeography and food availability as predictors of mesoscale among‐site variation in blue tit (Cyanistes caeruleus) nestbox occupancy and two components of productivity (clutch size and fledging success). We found that habitat was not a significant predictor of occupancy or clutch size but that occupancy exhibited pronounced biogeographic trends, declining with increasing latitude and elevation. However, fledging success, defined as the proportion of a clutch that fledged, was positively correlated with site level availability of birch, oak and sycamore, and tree diversity. The lack of correspondence between the effects of habitat on fledging success versus occupancy and clutch size may indicate that blue tits do not accurately predict the future quality of their breeding sites when selecting territories and laying clutches. We found little evidence of spatial autocorrelation in occupancy or clutch size, whereas spatial autocorrelation in fledging success extends over multiple sites, albeit non‐significantly. Taken together, our findings suggest that the relationship between breeding decisions and breeding outcomes varies among habitats, and we urge caution when extrapolating inferences from one habitat to others. This article is protected by copyright. All rights reserved.
Article
Supplemental food enables some birds to lay eggs earlier, perhaps by allowing birds to increase their energy intake or allocate energy from other activities to reproduction. We examined the relationships between prelaying behavior, food handling and consumption rates, and the timing of breeding of female Florida Scrub-Jays (Aphelocoma coerulescens) in suburban and wildland habitats. Scrub-jays in suburban habitats had access to ad libitum human-provided foods; wildland jays did not. During both years of this study, suburban scrub-jays bred earlier than their wildland counterparts. Wildland scrub-jays bred earlier in 1997 than in 1996, but the timing of breeding by suburban scrub-jays did not vary between years. Suburban scrub-jays spent less time foraging and more time perching than wildland jays. They handled more food per hour and per foraging hour, suggesting their foraging was more efficient. Despite this, food consumption rates did not differ between the two habitats. Neither time spent foraging or perching nor food consumption rates significantly influenced variation in time of breeding among individuals. Time of breeding was significantly influenced by site, year, and rate of food handling. Individuals that handled more food items per foraging hour, that is, those individuals that were most efficient, were the earliest breeders in both habitats. These results suggest that foraging efficiency increases with access to human-provided food and that resource predictability may be a perceptual cue for the appropriate timing of breeding. Variación en el Comportamiento de Forrajeo, la Dieta y la Época de Reproducción de Aphelocoma coerulescens en Ambientes Suburbanos y Silvestres Resumen. El alimento suplementario le permite a algunas aves poner huevos más temprano, quizás aumentando su ingestión de energía o permitiendo cambiar la asignación de energía de otras actividades a la reproducción. En este estudio examinamos las relaciones entre el comportamiento pre-postura, la manipulación de alimento y la tasa de consumo con la época de reproducción de hembras de la especie Aphelocoma coerulescens en ambientes suburbanos y silvestres. Las aves en ambientes suburbanos tenían acceso a alimento provisto ad libitum por humanos, mientras que las aves de las áreas silvestres no. Durante los dos años de estudio, las aves suburbanas se reprodujeron más temprano que las de las áreas silvestres. Las aves de áreas silvestres se reprodujeron más temprano en 1997 que en 1996, pero la época reproductiva de las aves de áreas suburbanas no varió entre años. Las aves suburbanas pasaron menos tiempo forrajeando y más tiempo perchadas que las de áreas silvestres, y además manipularon más alimento por hora y por hora de forrajeo, lo que sugiere que forrajearon más eficientemente. Sin embargo, las tasas de consumo de alimento no difirieron entre los dos ambientes. La variación entre individuos en el momento de la reproducción no fue influenciada significativamente por el tiempo invertido en forrajeo o descanso ni por la tasa de consumo de alimento, pero sí por el sitio, el año y la tasa de manipulación de alimento. Los individuos que manipularon más ítems alimenticios por sesión de forrajeo (los más eficientes), fueron los que se reprodujeron más temprano en ambos ambientes. Estos resultados sugieren que la eficiencia de forrajeo aumenta con el acceso a alimentos provistos por humanos y que la predecibilidad de los recursos podría ser percibida como una señal indicadora del momento de reproducción adecuado.
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Aphids are renowned plant parasites of agriculture, horticulture and forestry, causing direct physical damage by sucking phloem and especially by transmission of plant pathogenic viruses. The huge yield loss they cause amounts to hundreds of millions of dollars globally, and because of this damage and the intense efforts expended on control, some 20 species are now resistant to pesticides worldwide. Aphids represent an ancient, mainly northern temperate group, although some species occur in the tropics, often as obligate asexual lineages or even asexual ‘species’. However, besides their notoriety as enemies of plant growers, aphids are also extremely interesting scientifically, especially at the molecular and genetic levels. They reproduce mainly asexually, one female producing 10–90 offspring in 7–10 days and therefore, theoretically, could produce billions of offspring in one growing season in the absence of mortality factors (i.e. climate/weather and antagonists). In this overview, we provide examples of what molecular and genetic studies of aphids have revealed concerning a range of topics, especially fine-grained ecological processes. Aphids, despite their apparently limited behavioural repertoire, are in fact masters (or, perhaps more accurately, mistresses) of adaptation and evolutionary flexibility and continue to flourish in a variety of ecosystems, including the agro-ecosystem, regardless of our best efforts to combat them.
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This study investigated how Crimson Rosellas Platycercus elegans (CR) and Australian King-Parrots Alisterus scapularis (AKP) used provisioned seed at two public bird feeding sites in Australia. A total of 197 CR and 72 AKP were trapped and colour-banded. Observational data was collected every 10mins between 08:00-16:00 for three consecutive days during autumn and spring. Foraging effort was described using five metrics that quantified the birds’ visiting frequency and foraging duration over each day and observation period. Seed selection (over 5mins) and intake (over 10mins) were determined, and the energy intake was calculated. Total counts and population estimates were calculated for each species. Individual, species, seasonal and geographic variation in the use of provisioned seed was demonstrated by the metric summaries and Restricted Maximum Likelihood Modelling. Both species fed as part of large mixed species flocks that would not naturally congregate together to forage. Overall, CR were found to have higher foraging effort and feed in greater numbers than AKP, but a spectrum of use was observed for both species. Individuals were observed using the provisioned seed between 0-3 days/observation period. When birds used the provisioned seed, they were found to make between 1-8 visits/day, with most lasting 10-30mins. Few daily durations lasted longer than 50mins. Within a 10-minute interval, it was possible for a CR and AKP to obtain between 1.73-62.91% and 6.84-88.54% of their daily energy requirements, respectively. In a visit, either species could fill their crop and meet most, if not all, of their daily energy requirements. A small percentage of birds (6.5%) were found to use the feeding sites daily and for long durations (up to 160mins). It is likely that a proportion of the birds using the provisioned seed at both sites were dependent on the food source and would be at risk if the seed supply were suddenly reduced. The study also provided evidence that wild bird feeding provided an advantage to one or more species, as well as evidence that the food source did not affect the study species’ seasonal dispersal patterns or juveniles’ ability to forage on natural food sources.
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Parental behaviour of Blue Tits Parus caeruleus was video-recorded and analysed in an insular Mediterranean population that is believed to be adapted to food-limited conditions of an evergreen woodland. The population undergoes high external parasitism by blowflies (Protocalliphora). Contribution of male and female mates to parental care of nestlings was assessed when the nestlings were 13 days old (fledging takes place 21-22 days after hatching) to examine whether the sexes differ in their parental roles. Males brought a higher proportion of caterpillars, the optimal food for nestlings, than females. The caterpillars delivered by males were also larger. We suggest that males were more selective than females in prey choice because females were more time-constrained as they spent more time at the nest and their visit rate was higher. In addition to feeding nestlings, female Blue Tits perform nest sanitation and mending at all nestling stages. The only aspect of nest sanitation shared with males is the removing of faecal sacs, this activity being done by the males at a higher rate than in the case of females. We suggest that in the studied Blue Tit population, the sex differences in prey selectivity and feeding frequency result from the fact that females have to undertake especially intensive nest sanitation in response to high blowfly infestation. We would expect different patterns of parental care in non-parasitised populations living in rich habitats.
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We surveyed the extent to which householders in two suburbs of Cardiff provide food for birds. Up to 75% of households put out food in winter, but only 40% in summer. There is no significant difference in the types of food provided in winter and summer. Bread was the commonest item, being provided by 90% of households in both seasons. Food is usually thrown on the ground, although 25-30% of homes use bird-tables and peanut holders.We observed the attendance of birds at a peanut feeder over the course of a year. Female House Sparrows fed there more than males in early spring. House Sparrows, Great Tits and Blue Tits, especially juveniles, used it most in late summer. We suggest that those interested in the welfare of garden birds should provide more food in August and September.
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Bill characters were more variable than other linear characters measured. Bill-length and depth were strongly sexually dimorphic; differences were greater when body-size was kept constant. A study of feeding efficiency suggested that the optimal bill-shape should change between seasons in relation to the proportion of invertebrates in the diet. Birds with relatively deep bills were significantly faster at handling beechmast but slower at handling mealworms than relatively thin-billed birds. Winter flock observations showed that when the feeding environment was sufficiently varied, females fed both in a different way to, and significantly higher than, males. Bill-size varied within winters, closely tracking the percentage of beechmast in the diet. Dominance probably plays a key role in determining the niches available to subdominants. -from Author
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1. A study on the feeding ecology of the nestling Great Tit was carried out in the evergreen broadleaved forest from 1975 to 1979. The food consumption, excreting rate, body weight increment and maintenance cost were measured in the dry matter weight and calorific content.2. A nestling consumed 0.5g. dr. of food per day at the second day and attained at the maximum value, 1.3g. dr., at the tenth day. The mean food consumption of a nestling more than ten days old was 5.56g. fr. or 38% of the body weight. Total amount of food consumed for fifteen days from hatching to fledging was 65.65g. fr. per nestling. The food consumption was not correlated with the brood size. The amount of feces excreted per nestling per day was 2.0, 5.6 and 8.2g. dr. at the fourth, eighth and fourteenth days, respectively. The assimilation rate varied between 26% and 57% of the ingested dry matter. The growth rate attained to the maximum value, 0.34g. dr./day, at the fifth day. The maximum maintenance cost was 0.5g. dr.3. The food consumption was 3.7, 6.0 and 7.0 Kcal at the fourth, eighth and fourteenth days, respectively. The excreting rate was 0.7, 1.7 and 2.8 Kcal at the fourth, eight and fourteenth days, respectively. The assimilation rate varied between 52% and 72% of the ingested energy. The maximum maintenance cost was 4.4 Kcal.4. Each of the food consumption, excreting rate and maintenance cost was greater in the present study than the respective values obtained in the larch wood by Royama (1966). The high ambient temperature in the ever-green broadleaved forest seems to be concerned with these differences.
Article
Parus major and P. caeruleus breeding in suburban gardens were studied in areas of N Cardiff, S Wales. There was a higher density of mature native trees in Cyncoed than Heath. Density of blue tits breeding in Cyncoed was 13.7 pairs/10 ha, similar to densities recorded in deciduous woodland. Density of great tits in both areas was low, and blue tits were c3 times as numerous. Both species suffered a reduction in breeding success, rearing about half as many young as comparable populations breeding in deciduous oak woodland. Most of the reduction was due to nestling mortality from starvation. Great tits in gardens began breeding earlier than those in woodland; blue tits did not. In 1981 and 1982 blue tit breeding success declined throughout the breeding season. In 1983 there was no such relationship. High rainfall around the time of peak hatching in Cyncoed is though to explain the poor breeding success in this area during 1983. In 1981, when blue tits began breeding earlier than in subsequent years, there was a relationship betweeen breeding success and density of trees within 25 m of the nest. There was evidence of interference in nestbox selection between blue tits at distances of 40-50 m, but no evidence of interference in great tits or between the 2 species. -from Authors
Article
1. Observations in Scots (Pinus sylvestris) and Corsican (P. nigra) pine plantations of Thetford Chase, Norfolk, during five breeding seasons 1952-56, describe the food, food stock and feeding habits of great tits (Parus major), blue tits (P. caeruleus), coal tits (P. ater) and willow tits (P. montanus). 2. The density of tits breeding in nest-boxes is recorded. Coal tits, adapted to conifers, were much the commonest species; great and blue tits, adapted to broadleaved woods, bred commonly in the pine only where there were nest-boxes; willow tits were scarce and rarely bred in nest-boxes. 3. The food of the young was recorded by direct observation and identifications were checked from meals collected with an artificial nestling gape. Numerically, caterpillars formed about 50% of the food of early and late broods combined. Caterpillars from Scots pine important for early broods were Evetria spp. (Eucosmidae) from buds and shoots, Thera obeliscata (Hydriomenidae) and Ellopia prosapiaria (Selidosemidae) from pine needles; all of which were virtually absent from Corsican pine. For late broods, caterpillars of Panolis griseovariegata (Caradrinidae) from both Scots and Corsican pine were much the most important prey. 4. Typically, the caterpillar stock in pine was low (especially in Corsican pine) in April and May, increased slightly in June, and reached a peak in late summer. This contrasted with broadleaved woods, where the stock was greatest in May-June when early broods of tits were in the nest. 5. Great, blue and even coal tits nesting in the pine collected much food for early broods, but little for late broods, from scattered broadleaved trees up to 400 m from their nests; and those in Corsican pine plantations also foraged in distant Scots pine. Caterpillars from sources other than pine formed the largest group in the diets of early broods of great and blue tits, but were less important for coal and willow tits. 6. Proportions of different prey species fed to the young varied greatly each year. The diet of early broods of great tits was characterized by the absence of Evetria larvae. Spiders and insects other than Lepidoptera were taken more often by coal tits than by great or blue tits. Large caterpillars, notably Panolis, were much more prevalent in the diet of late than of early broods of great tits; but the diets of early and late broods of coal tits were broadly alike (too few late broods of blue tits for comparison). The diet of great tits was always more varied than that of the other species, but especially so in the pine; that of blue tits was broadly similar in pine and broadleaved woods. 7. All tits selected larger prey than those available at random in the pine. Great tits selected larger prey than did blue tits, and blue tits than coal tits; and even when feeding on the same prey species on the same dates and in the same plantations as coal tits, great tits invariably selected the larger specimens. 8. In the pine, great tits breed on dates and lay clutches appropriate to the broadleaved woods to which they are adapted; but whereas in broadleaved woods early broods do better than late broods, because food is more abundant, the reverse happens in the pine where feeding improves later in the season. In the pine, early broods of great tits were short of food, but late broods not. 9. Each member of a late brood of coal tits received much more food than did each of an early brood, but this was not reflected in their weights: presumably neither early nor late broods were short of food. Though adapted to conifers, coal tits are more productive breeding in broadleaved woods. They remain scarce in broadleaved woods probably because unsuccessful in interspecific competition for food in winter. 10. The numbers of caterpillars eaten represented only a few per cent of those present. One exception was in Scots pine from 1 May to 15 June 1956, when coal tits alone ate some 48 000 Evetria larvae or pupae per 10 ha (25 acres), representing about 20% of the stock. Despite the usually low percentage predation, intraspecific competition for food in summer may account for the modest decline in average clutch size with increasing density of birds. In summer, tits are unlikely to eat a large part of their food stocks or perceptibly influence the numbers of their prey, because each prey species is available for only a short period. Percentage predation is likely higher in winter, but on a different array of species. 11. Nest-boxes influence the local distribution of, especially, great and blue tits in pine in summer, but probably do not increase their overall populations--determined by food shortage in winter. Together, pine and broadleaved trees provide a sustained food supply throughout the summer. Hence selected broadleaved trees interspersed through the pine plantations might both enable more tits to survive the winter and improve their breeding; and so in turn enhance the general level of bird predation on forest insects.
Article
When the CHI **2 test for independence between rows and columns in a two-way contingency table is significant, a procedure is described for sequentially identifying those cells which contribute heavily to the CHI **2 statistic. A 14 multiplied by 14 contigency table is used to compare the graphical technique of S. E. Fienberg with this method. An algorithm is presented to estimate the expected values of each cell under the model of quasi-independence.
Article
(1) This paper deals with the underlying mechanisms of the hunting behaviour and selection of prey species by great tits feeding their young at the nest, and is based on observations made mainly in mixed broad-leaved woodland in Wytham near Oxford, England, and partly in larch plantations in Yamanaka, Japan, using both automatic cameras (41 000 photographs taken) at ten nests for 150 nestling-days and direct observations at six nests for 63 nestling-days. (2) A brief description of general tendencies in nestlings' diet as observed by various authors in different parts of the world is given first, as an introduction to this study. The major prey species in the breeding season are invariably Lepidoptera, particularly the larvae. (3) Apart from spiders taken during the first few days after hatching, the composition of prey species in the diet of nestlings has no particular relation to their age. It is suggested that spiders are of particular importance, from a nutritional point of view, at a certain stage of the chicks' growth. The nestlings were regularly fed with grit and snail shell, whose function seems to be related solely to mechanical grinding of food in the gizzard. (4) The seasonal succession of the prey species in the nestlings' diet throughout the breeding season is described, and the collection sites for many of the prey species are discussed. (5) Factors governing the utilization of prey species by tits to feed their young are highly complicated and are discussed first in terms of observed facts. On the whole, there seems to be no direct correlation between the biomass of the prey in the habitat and the tits' selection. The occurrence, in the nestlings' diet, of many lepidopterous species coincided with their time of pupation, which suggests that the behaviour of the prey has some importance in relation to their exposure to predation by tits. The effects of taste and conspicuousness of the prey species and of alternative prey occupying different micro-habitats are discussed in relation to the hunting efficiency of tits. (6) The factors governing the utilization of prey by tits are discussed further with the aid of a theoretical model. Tinbergen's theory of search images is critically reviewed, and an alternative theory proposed. The model is based on one fundamental assumption: that the predator tries constantly to maximize its hunting efficiency within its limited ability to perceive the abundance of food in various parts of the hunting area. (7) The concept of `profitability', defined as the amount of food the predator can collect for a given amount of hunting effort, is introduced into the model, and the relationship between the profitability and the density of a given prey species is investigated. From this model, some conclusions are drawn, and tentatively tested against the available observations. As the profitability of a prey species is determined not only by the density but also by the size of the prey and the method of hunting of the predator, and as the predator tries to get the most out of the whole complex of prey populations in the habitat, a direct correlation between the numbers of a given prey taken by the tits and its density cannot be expected. Instead, it is shown that the tendency expected from this model fits, without apparent contradictions, both Tinbergen's observations and my own. (8) It is also shown that the size of prey has some bearing on the selection of food by tits and influences differences in the composition between the diets of adults, fledglings and nestlings. (9) Some suggestions are made in concluding remarks as to the aspects of the problem which need to be considered in future studies.
Article
1. The possible competition for food between the great and blue tit (Parus major and P. caeruleus) in oak woodland, and their relationships with the coal and marsh tit (P. ater and P. palustris), was studied by means of gizzard analyses. There was little similarity in the diets of the great and blue tits, the great tit taking mainly adult insects, especially weevils, while the blue tit fed mainly on scale insects and small larval and pupal forms. The coal tit showed a preference for small free-living insects, and scales. The diet of the marsh tit consisted of adult insects, scales and some larval forms. Spiders formed a small proportion of the diet of all four species. The great and marsh tits fed more on seeds and nuts than did the other species, and oak bud and gall tissue were found in large quantities only in the blue tit. 2. An analysis of the insect food showed that the great tit was largely a ground feeder, except in the breeding season, while the blue tit fed mainly on the oak twigs, buds and leaves. The coal tit showed a preference for insects from trunks and branches, while the marsh tit fed both on the ground and in the canopy. The beaks of the tit-mice were adapted to the size and types of foods taken by the birds, enabling all four species to feed in the same places without necessarily competing for food. 3. Nestling foods of a brood of great tits and a brood of blue tits reflected the differences in the type and size of foods selected by the adults in the rest of the year. Caterpillars were taken by both species, but pupae extracted from curled leaves formed a much greater proportion of the diet of the blue tits than of the great tits. Adult insects, forming 19% of the great tit nestling food, were not taken for the young by the blue tit. Both species fed spiders, crushed snails and grit to the young. Most of the food items brought to the young blue tits measured under 10 mm, while most of those fed to the great tits measured over this length. 4. Measurements were made of the caterpillar and titmouse populations in a nest-boxed area and an adjoining unboxed control area in 1950 and 1951. The rate of predation by titmice on all defoliating caterpillars in the boxed area was about 1.4% in 1950, 4.8% in 1951, while in the control area it was 0.9% in 1950, 3.2% in 1951. The proportion of the winter moth (Operophtera brumata) larvae removed by the titmice in the two years in the nest-boxed area was 0.5% in 1950, 2.6% in 1951, and in the control area 0.3% in 1950, 1.7% in 1951. In both years the caterpillar population was relatively low compared with the 1949 populations. In the winter of 1950-51 it was estimated that the predation rate by titmice on the female winter moths might have been about 20% in both areas. This predation on the moth population may be affected by climatic conditions, and the abundance of alternative food for the birds.
Article
Recent theoretical and field work on communities of interacting species has employed various forms for estimating the competition matrix elements, @a"i"j, from utilization coefficients p"i"a (which measure the relative utilization of the @ath resource category by the ith species). Some little-known properties of these forms are discussed. When more than one resource dimension is involved, there is in general no substitute for measuring the species' full multidimensional utilization functions; a critical discussion is given of the estimation of such multidimensional competition coefficient @a"i"j by products of one-dimensional coefficients.
Article
. 1 The breeding biology of Parus major and P. caeruleus was studied in 1947–49 in a mixed deciduous wood, near Oxford, in which 200 nestboxes were erected (density about two per acre).2 The combined Great and Blue Tit population rose from about 43 pairs in 1947 (following a very severe winter) to about 100 pairs in 1948, and about 135 pairs in 1949. Of these, nearly all the Great Tits and about two-thirds of the Blue Tits nested in the boxes.3 Pre-nesting behaviour is briefly described; hole inspecting and courtship feeding were observed. The average time taken to build a nest differed in each season; both species built many more nests than were used for laying.4 The breeding dates differed by two to three weeks in different years. The exact season is linked to the brief period of abundance of the larvae of Cheimatobia brumata and Hibernia defoliaria, on which the nestlings are largely fed. The seasonal rise and fall in the larval abundance were estimated by measuring the volume of faecal pellets from the larvae.5 The average clutch-size differed significantly from year to year. Clutches laid early in the season were on average larger than those laid later. Repeat clutches were smaller than first clutches, and genuine second clutches were smaller still.6 Individual egg-weights of the Great Tit ranged from 1.3 to 2.2 grams, and averaged 1.75 grams (no significant difference between years). Eggs from average-sized clutches were heavier than those from very small or very large clutches. The first four to six eggs laid in a clutch tended to be successively heavier, but in general eggs in each clutch tended to be of similar weight. Clutches of the Blue Tit were weighed in one year only; the average individual egg-weight was 1.11 grams.7 Incubation tended to begin earlier, in relation to clutch completion, in late nests than in early ones. The mean incubation period of the Great Tit was 13.9 days, and of the Blue Tit 14.2 days.8 The mean growth rates of Great Tits differed significantly in 1948 and 1949. The growth curve of Blue Tits is similar to that of the Great Tit.9 Members of large-sized broods averaged significantly lighter than members of small-sized broods, and second-brood nestlings were lighter than first-brood nestlings. Great Tit nestlings aged 14 1/2 days ranged in weight from 10.2 to 21.4 grams. Less than 1% of the nestlings in first broods died from starvation in the nest, but there were many losses in second broods.10 Eggs laid after the start of incubation hatched later than the rest of the clutch. Late-hatched nestlings averaged significantly lighter than the others.11 Frequency of parents' visits to the nest increases with number in brood, but not proportionately. Hence a member of a small-sized brood receives on average more food visits than a member of a large-sized brood.12 Feather development was independent of body-weight, and is therefore a reliable indicator of age.13 The mean nestling period of the Great Tit was 18.9 days, of the Blue Tit 19.7 days.14 When losses due to man are excluded, the breeding success was about 90% for each species.
Article
(1) Great tit and blue tit breeding densities in Wytham Wood, Oxfordshire were examined. Annual fluctuations in the great tit population were intra- and interspecifically density dependent but the blue tit population appeared to be only intraspecifically density dependent. (2) Great tit breeding success, as measured by the mean fledging weight of each chick in a brood, was negatively correlated with the density of blue tits. (3) The nestling diets of blue and great tits were very similar. (4) An area of woods from which all blue tit young were removed at hatching had significantly heavier broods of great tits when compared with a control area. (5) Interspecific and intraspecific competition for food during the breeding season have been significant factors contributing to density dependent limits on reproductive success in great tits. The competition for insect food by breeding birds in temperate regions may be an important source of diffuse competition.
Article
Observations were made on feeding rates and food-consumption of nestling Great Tits Parus major mainly in Larch plantations at lake Yamanaka, Japan.Feeding frequencies were recorded by an automatic recorder. There were marked differences between early and late broods; the feeding frequencies were twice as great in early than in late broods of the same size. No clear tendency was observed in the variations of feeding frequencies in relation to brood size. There was, however, a clear inverse relationship between the frequencies and the average size of food brought to the nests. The males' share in terms of feeding frequencies is described. These figures, however, did not follow the males' contribution in terms of weight of food, which was nearly always higher than the females'. It is pointed out that feeding frequencies are far too variable to be used as a true index of food consumption by nestlings, and are not reliable.Attempts were made to measure the weight of food; the method is described. The average weight of food brought by males was lighter in early than in later broods. The total weight of food was estimated. The trend of daily food consumption per chick was similar to that of the chick's growth curve. It was found that up to about the tenth day of the nestling period daily food-intake per chick increased linearly as body weight increased.At some nests, rate of defaecation was observed. This was at first low, but it increased steeply on the third day, with a steady increase thereafter.By comparing the rates of food intake, faeces output, and weight increment of a chick, it was found that only 20–30% of digested matter (the difference between food-intake and faeces-output was used up daily (for body temperature regulation various external effort, etc.). The factors responsible for this high efficiency of growth in nestlings are discussed.There was a clear inverse relationship between the total weight of food brought per chick per day and the brood size. This is largely because the heat-loss is greater in small than in large broods, so that a chick from a small brood in fact needs more energy to maintain its body temperature after a certain age than one from a large brood. This is discussed in detail.Factors which caused variations in size of food are discussed in relation to feeding frequencies.It is pointed out that, because of the inverse relationship between energy requirement by each chick and brood size, the total food requirement by a brood as a whole did not vary directly in proportion to the brood size. An estimation showed that a b/3 still required about 75% of the total food required by a b/8. A smaller brood is less advantageous than expected to parents feeding nestlings when they encounter adverse conditions, e.g. food shortage in the habitat, or a lack of help by their mates, etc. On the other hand, it is suggested that once they have left the nest, the food-demand by a brood of fledglings the parents have to feed, so that, in the fledging period, in times of food shortage it would certainly be advantageous to have fewer young. It is suggested that, although fledglings may consume three to four times as much food as nestlings, the parents, in providing this food, would not work proportionately harder, since the parents' efficiency of providing food could be higher in feeding the fledglings, which always follow the parents as they are hunting, than in feeding the nestlings to which food has to be brought.On this basis, the adaptive significance of the length of the nestling period in nidicolous species is discussed in relation to clutch size, brood size and food requirement.
Article
1. To examine the ultimate factors determining the frequency with which male and female blue tits (Parus caeruleus) feed their nestlings, I manipulated the brood sizes of 34 pairs breeding in Wytham Woods, England, and recorded automatically the number of visits when the young were 11–13 days of age. At this time adults were caught and weighed and the nestlings weighed. 2. The number of visits/brood increased linearly with brood size, with no evidence of an upper limit to brood feeding frequency. The number of visitsnestlings-1day-1 decreased from 138 to 108 as brood size increased from 3 to 6, but levelled off at 68–87 visits/nestling as brood size increased from 8 to 15. 3. Female weight-loss during the nestling period increased linearly as the feeding frequency of the brood increased: those females were lightest that fed their young most often; this is of some significance since I previously showed that the lightest females are least likely to survive to the following year. The correlations of feeding frequency with brood size and feeding frequency with female weight are sufficient to account for the commonly observed correlation of brood size and female weight. No relationship between feeding frequency and male weight dynamics was apparent. Feeding frequency of the brood increased as mean nestling weight decreased. Apparently, parents compensate, in part, for low nestling weight by increasing feeding frequency. Low nestling weight, in turn, has proven detrimental to post-fledging survival. 4. Lack's (1947, 1954) hypothesis, that the decline in visits/nestling as brood size increases reflects the inability of parents to sustain high brood feeding rates, is refuted by the observations made in this and a large number of other studies. Royama's (1966) hypothesis that the observed decline in visits/nestling reflects a decrease in energy needed to maintain homeothermy, receives some support. Behavioral and physiological studies, however, suggest that the Royama effect is limited to small broods (c. four or fewer young). 5. I propose, instead, a model of optimal feeding frequency, which accounts for observations made by myself and others, and which incorporates Royama's hypothesis as well. The model assumes that parents optimize their investment in their young. On the one hand, an increase in feeding frequency means more food for the young, which enhances offspring survival (benefit); on the other hand, increased feeding frequency is costly to the parents (reduces parental survivorship). Natural selection favors breeding individuals that maximize the difference between benefits (to the offpsring) and costs (to the parents). The model accounts for many aspects of blue tit reproductive biology, including the observed relationship between nestling weight and brood size and the observation that parent reproductive costs increase with brood size.
Land Use and Living Space The food of titmice in oak woodland
  • Feeding
  • R H Best
Feeding ecology of suburban titmice Best, R. H. (1981). Land Use and Living Space. Methuen, London. Betts, M. M. (1955). The food of titmice in oak woodland. Journal of Animal Ecology, 24, 282-325.
The Future of Forestry. British Association of Nature Conservationists
  • R H Grove
Grove, R. H. (1983). The Future of Forestry. British Association of Nature Conservationists, Cambridge, U.K. Kluijver, H. N. (1950). Daily routines of the great tit (Parus major). Ardea, 38, 99-135.
A device of an auto-cinematic food recorder
  • C M Perrins
Perrins, C. M. (1979). British Tits. Collins New Naturalist, London. Royama, T. (1959). A device of an auto-cinematic food recorder. Tori, 15, 172-176.
The Future of Forestry British Association of Nature Conservationists Daily routines of the great tit (Parus major)
  • R H Grove
  • U K Kluijver
Grove, R. H. (1983). The Future of Forestry. British Association of Nature Conservationists, Cambridge, U.K. Kluijver, H. N. (1950). Daily routines of the great tit (Parus major). Ardea, 38, 99-135.