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Adult Squacco Heron pecking and capture rates (means ± 95% confidence limits) by calendar period (A: 26 June-9 July; B: 10-20 July; C: 21 July-3 August). Sample sizes are indicated above or next to their respec- tive sample means.
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The foraging behavior of adult and recently fledged juvenile Squacco Herons (Ardeola ralloides) was studied during the breeding season at the Axios Delta, northern Greece. Adults were more efficient foragers than young birds and they had a 37% higher success per peck rate. The majority of adults captured some large prey items, while most juveniles...
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... rates are probably related to the fact that they caught smaller prey items than adults. A similar association was found in adults, over the three observation periods: foraging rates were significantly higher in the first period (Fig. 1), when a significantly greater proportion of birds caught only small prey. Food intake rate depends both on capture rate and on prey size (Dimalexis et al. 1997; Campos and Lekuona 2001). Herons which capture small prey may need to in- tensify their foraging rates, in order to meet dietary demands. At the same time, the foraging rates of individuals which capture large prey may be constrained, because the pursuit and capture of such prey is often more time-consuming (Dimalexis et al. 1997; Wong et al. 2000). A smaller proportion of adults caught large prey in the first observation period, and this may be because such prey were less available at that time. Seasonal variation in heron food type and size often reflects changes in prey availability (Matsunaga 2000; Richardson et al. 2001). Another possi- bility is that in the first period, a greater proportion of adults selected small prey, because they were feeding small nestlings that could not swallow large items (Moser 1986; Campos and Lekuona 1997). We found no significant seasonal variation in juvenile data. The foraging skills of juvenile herons often improve with increasing age and experience (Rodgers 1983), even over weekly intervals (Quinney and Smith 1980). One reason why we did not observe any such trend over 25 days of observation may have been because the feeding skills of juvenile Squacco Herons develop slowly, although it was evident that newly fledged, inexperi- enced birds were continually added to the foraging juvenile group, thus keeping the average feeding performance at a low level. The foraging behavior of adult and juvenile Squacco Herons varied little and non- significantly between morning and evening. The feeding activity of herons in estuaries is usually affected by the tidal cycle, and is often independent of time per se (Richner 1986; Matsunaga 2000). In non-tidal habitats, ardeids may vary their foraging ...
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... At this time, herons take prey for their own use, as opposed to the breeding season, when the feeding of chicks requires a greater frequency of catches. The observations focused on feeding birds and were made only on sunny days, between 09:00 and 17:30 h local time, when conditions were favorable for observing foraging herons (see Hafner at al. 1982;Papakostas et al. 2005;Nefla and Nouira 2016). The weather conditions were similar on all the observation days, with temperatures hovering around 30 °C and no precipitation or strong winds that might affect the birds' behavior. ...
... The weather conditions were similar on all the observation days, with temperatures hovering around 30 °C and no precipitation or strong winds that might affect the birds' behavior. Observation methods were developed based on previous behavioral studies of herons with modification due to the specific foraging characteristics of the studied species and their foraging sites (see Dimalexis et al. 1997;Papakostas et al. 2005;Takaki and Eguchi 2008). The observers used 10 × 42 binoculars and 40-60× spotting scopes to watch the birds and to determine the size of prey, and a dictaphone to describe the herons' behavior. ...
... In herons, changes in foraging strategy may depend on biological features like body size (Nota 2003;Papakostas et al. 2005). They also modify their tactics to suit local conditions (Nefla and Nouira 2016). ...
The composition of assemblages, diet and behavior of waterbird species with similar ecological features are important aspects in the functioning of aquatic ecosystems. Closely related animal species often share resources such as space and food in ways that reduce competition, but if the diets of different species strongly overlap, interspecific competition may intensify. This analysis examined behavioral data relating to Great Egret, Little Egret, and Squacco Heron to explore their foraging efficiencies in rich aquatic habitats in an arid zone during post-breeding movements. The fieldwork was carried out in small estuaries of a Wadi on the southern coast of Oman. The frequency of interactions was the highest in Squacco Heron and the lowest in Great Egret. However, the differences in the numbers of inter- and intra-specific interactions between the 3 species were significant. Activity indices calculated for a 5-min period, i.e., the number of interactions (interaction index) and times of flying and walking (movement index) differed among the 3 species. The number of successful attacks was the highest in Squacco Heron, while the foraging effectiveness of Great Egret and Little Egret was similar. GLM analysis showed that only the movement index was significant, as it had a positive impact on individual foraging success. Great Egret caught more fish than the other 2 heron species which, in turn, caught a greater number of smaller prey items, mostly invertebrates. This study shows that heron species in the same rich habitat employ different foraging tactics. In comparison to the other two heron species, the foraging tactics of Squacco Heron seem to be the most susceptible to competition. However, its greater mobility and using different foraging tactics, enhance its foraging success.
... Thus, the competitive effect of large fish may be more pronounced in the later stages of chick growth, affecting the near-fledging young which are starting to forage on their own whilst they are still confined to the natal pond. The inexperienced young may be particularly vulnerable to the scarcity of small prey items: compared to adults, juvenile herons are known to exploit smaller prey (Papakostas et al. 2005). ...
Knowledge of the relationships between food habits and habitat is crucial for the assessment of habitat quality for birds. The
present study investigated the diet and reproductive success of Little Bitterns Ixobrychus minutus nesting on cyprinid fish
ponds, an important breeding habitat of this species in central and eastern Europe. Being subject to different management
practices, fish ponds provide food resources of uneven availability for this small heron. Prey items regurgitated by nestlings
were examined, and breeding success was estimated on monoculture ponds stocked either with small fish (of a size suitable
for feeding nestlings) or large fish (unavailable to Little Bitterns and adversely affecting their non-fish prey), on abandoned
ponds dominated by small fish but with large fish also present, and on angling ponds dominated by large sport fish but harbouring
significant numbers of small fish as well. A total of 1356 prey items from 78 broods were identified. Although Little
Bitterns exhibited dietary flexibility in response to the contrasting availability of prey on their nesting ponds, the bulk of
the nestlings’ diet consisted of fish. The size of fish brought to the nest increased significantly with brood age, showing that
parents adjusted the prey size to the gape constraints of their young. The chick production determined for 73 broods did not
differ with respect to pond management, but the dietary composition indicated that to compensate for food shortages, birds
nesting on ponds containing mainly large fish made foraging flights to food-richer ponds. The abundance of small-sized fish
prey may be a factor limiting the breeding success of small- and medium-sized predatory waterbirds and should be taken
into consideration in management strategies of habitats dominated by fish.
... Similarly, the foraging success of Snowy Egrets (Egretta thula) has been found to be affected by water depth, while the foraging success of Great Egrets (Ardea alba) was less dependent on water level (Gawlik 2002;Maccarone and Brzorad 2007). Several studies have been conducted on tidal influence on foraging activities of waterbirds in general (Burger et al. 1977;Engelmoer 1982;Matsunaga 2000;Maccarone and Brzorad 2005;Papakostas et al. 2005;Norazlimi and Ramli 2015;Calle et al. 2016). However, our study highlights the foraging strategies of one of the rarest herons in the world that prefers fast-flowing river with more water current as its foraging niche across its range including India. ...
... Studies on Grey Heron (Ardea cinerea), Great Egret (Dimalexis et al., 1997), Little Egret (Egretta garzetta) (Dimalexis et al., 1997;Wong et al., 2000) and Squacco Heron (Ardeola ralloides; Papakostas et al., 2005) have showed that when these species captured smaller prey, they had to increase their foraging rates subsequently to meet the required dietary needs. The above studies also demonstrated that species that captured larger fishes had lower foraging rates. ...
... However, pursuing larger fishes also consumes more time and energy. Thus, White-bellied Herons in NTR captured the majority of the smaller fishes while facing upstream, like other heron species (Britton and Moser 1982;Trexler et al. 1994;Papakostas et al. 2005), and larger fishes while facing downstream. Hence, from an energetic perspective, capture efficiency while consuming more smaller fishes masks the fact that more calories may have been gained facing downstream by consuming larger fishes. ...
The critically endangered White-bellied Heron (Ardea insignis) is a piscivorous visual forager that
prefers to forage in fast-flowing freshwater rivers. This study highlights White-bellied Heron foraging behavior in
the fast-flowing rivers of Namdapha Tiger Reserve during 2013–2017. The herons spent significantly more time and
also made more foraging attempts while foraging in shallow water (foraging time: 61.45 ± 15.55%; strike rate: 1.70
strikes/hr). Herons were more successful in catching fishes when they foraged facing upstream (capture rate: 0.62
fishes caught/hr) with increased capture efficiency (44.62%). White-bellied Herons caught the majority (60.98%)
of small sized fishes (≤ 9 cm) while facing upstream and the majority (60.92%) of large sized fishes (> 18 cm) while
facing downstream. These findings shed light on the manner in which this rare and critically endangered bird is
adapted to life on fast-flowing rivers and the importance of these unique places for its conservation.
... Fish size can play an important role in the choice of prey, and heron generally show a preference for larger prey (Britton and Moser, 1982;Feunteun and Marion, 1994;Gwiazda and Amirowicz, 2006). Various authors have suggested that juvenile heron are less successful at feeding and spend more time perfecting feeding skills than adults (Carss, 1993;Lekuona, 2002;Papakostas et al., 2005). Juvenile birds must learn to catch and handle prey in aquatic habitats (Voisin, 1991;Kushlan and Hancock, 2005). ...
The components of foraging behaviour and success of adult and juvenile Grey Heron Ardea cinerea were studied at the Dobczyce Reservoir (southern Poland) in July and September 2015. Juvenile and adult birds moved at similar rates during both months. Fish capture attempt rate was significantly higher for juvenile birds than for adults in July but not in September. Capture rate and foraging success probability (number of captures over all attempts) was significantly lower in juveniles in July but not in September. The foraging success probability of juveniles increased from July to September. Adult and juvenile birds caught mostly small fish, with no differences in size. However, handling time in juvenile birds was much longer than in adults in July but not in September, after controlling for differences in prey size. Thus, juvenile Grey Heron increased their efficiency of catching fish from July to September by reducing the number of mistakes, probably as a result of experience.
... Fish size can play an important role in the choice of prey, and heron generally show a preference for larger prey (Britton and Moser, 1982;Feunteun and Marion, 1994;Gwiazda and Amirowicz, 2006). Various authors have suggested that juvenile heron are less successful at feeding and spend more time perfecting feeding skills than adults (Carss, 1993;Lekuona, 2002;Papakostas et al., 2005). Juvenile birds must learn to catch and handle prey in aquatic habitats (Voisin, 1991;Kushlan and Hancock, 2005). ...
The components of foraging behaviour and success of adult and juvenile Grey Heron Ardea cinerea were studied at the Dobczyce Reservoir (southern Poland) in July and September 2015. Juvenile and adult birds moved at similar rates during both months. Fish capture attempt rate was significantly higher for juvenile birds than for adults in July but not in September. Capture rate and foraging success probability (number of captures over all attempts) was significantly lower in juveniles in July but not in September. The foraging
success probability of juveniles increased from July to September. Adult and juvenile birds caught mostly small fish, with no differences in size. However, handling time in juvenile birds was much longer than in adults in July but not in September, after controlling for differences in prey size. Thus, juvenile Grey Heron increased their efficiency of catching fish from July to September by reducing the number of mistakes, probably as a result of experience.
... The foraging activity of birds is necessary for their survival and reproduction, making it an essential aspect of the life of birds (Papakostas et al. 2005). Ardeid foraging is a multidimensional behavior; herons use a varied foraging repertoire to catch prey (Rodgers 1983). ...
... Year ever, in addition to using the "standing and wait" technique, Great and Little egrets also adopted the "walking slowly" technique (Hafner et al. 1982;Tojo 1996;Papakostas et al. 2005). Although Grey Herons have been described as "hunters on the lookout" (Krebs 1978), Little Egrets were the most active individuals among our studied species. ...
This study was carried out at Ichkeul National Park, Tunisia, during 2009 and 2010. The influence of environmental variables on the foraging behavior of three Ardeid species was studied. Grey Herons (Ardea cinerea) were the least active of the three species, having the greatest resting percentages in 2009 (55.0%) and 2010 (64.9%); they primarily used the “standing and wait” hunting behavior (68.5%). Great Egrets (A. alba) (93.6%) and Little Egrets (Egretta garzetta) (86.5%) primarily adopted a “walking slowly” strategy. Little Egrets also frequently used the “walking quickly” behavior, a more active hunting technique. Both Little and Great egrets varied their hunting behaviors according to water depth. In shallows, they used the “walking quickly” behavior, while in deeper waters they used the “standing and wait” behavior (Little Egret: r = -0.26, P < 0.001; Great Egret: r = -0.44, P < 0.01). For Little Egrets only, high temperature (F = 42.77, df = 1, P < 0.001) and high wind velocity (F = 63.81, df = 1, P < 0.001) promoted an active “walking quickly” hunting behavior, while high light intensity frequently promoted the “standing and wait” and “walking slowly” behaviors (F = 5.48, df = 1, P < 0.05).
... Several ecological studies have been conducted on foraging of herons and egrets. Feeding behavior and efficiency of ardeids are affected by several factors, including prey density and availability (Draulans 1987, Richard-son et al. 2001, time of year (Erwin 1985) and day (Fasola 1984, Kersten et al. 1991, bird age (Quinney and Smith 1980, Cezilly and Boy 1988, Papakostas et al. 2005, weather conditions (Quinney and Smith 1980), habitat characteristics Parsons 1994, Dimalexis et al. 1997), hydrological regimes including tidal cycles (Sawara et al. 1990, Strong et al. 1997, Matsunaga 2000, and social behaviors (Wiggins 1991, Master 1992. Additionally, the spatiotemporal variation in feeding efficiency of ardeids may reflect a difference in habitat quality and/or their physiological needs for nesting and survival . ...
... A significant difference was observed in the heron's moving rate according to breeding stage. Adult grey herons walked more during the fledging stage than during the incubating and nestling stages (Kruskal-Wallis test, (Quinney and Smith 1980, Lo and Fordham 1986, Burger and Gochfeld 1989, Papakostas et al. 2005). The lower feeding success of young herons may result from a lack of foraging experience (Draulans and van Vessem 1985, Burger and Gochfeld 1989, Marchetti and Price 1989 and sensorimotor maturity (Cezilly andBoy 1988, Marchetti andPrice 1989). ...
... Low feeding efficiencies of juveniles may affect their survival after fledging and also affect fat reserves for the autumnal migration. Temporal changes in the feeding efficiency of herons may be related to their breeding stage (Matsunaga 2000, Papakostas et al. 2005 and may also reflect changes in prey availability within the foraging range (Matsunaga 2000, Richardson et al. 2001. In this study, most grey herons were incubating eggs during the early period (from April to 10 May) and, therefore, only needed food for themselves. ...
To examine factors affecting feeding efficiency of grey herons (Ardea cinerea), the foraging behavior was studied at a reservoir in Asan city, Chungcheongnam-do, South Korea during the breeding seasons (from April to July) of 2006 and 2007. Four factors (age of foraging birds, time of day, breeding stage, and microhabitat type) were analyzed. Adults were more efficient foragers than recently fledged juveniles, and they had a higher success rate than juveniles. About half of the adults caught large prey, whereas most juveniles caught only small prey. Adult grey herons had different feeding efficiency according to the breeding stage. Pecking and capture rates were high during the late period (fledging stage), and biomass intake rates were high during the early (incubating stage) and late periods. However, time of day had no significant effect on foraging activity of adult grey herons. Feeding activities of adult grey herons also showed significant variation among microhabitat types. Pecking and capture rates were higher in the submerged plants area, but capture success rate and biomass intake rate were not different according to microhabitat type.
... n for understanding its ecology and physiology. For threatened species, such understanding is essential for habitat management and wildlife conservation, as food supply and quality affect breeding success and the size of bird colonies (Gwiazda and Amirowicz 2006;Enriquez et al . 2010). While the diets of many ardeid birds are well documented (e.g. Papakostas et al . 2005;Hall and Kress 2008), further studies are required on the feeding ecology of other species, especially those that are either threatened or depend on particular areas where marked fluctuations in food supplies are likely (Herrera et al . 2005;Taylor and Schultz 2008). In this study, we aim to: 1) provide a quantitative assessment of the n ...
Nestling diets of the vulnerable Chinese Egret (Egretta eulophotes) were analyzed at two breeding colonies on islands off Fujian, Southern China, in 2007 and 2008. Fish and shrimps were the main prey, comprising 87.5% and 35.4% by frequency of occurrence in regurgitations, respectively. Prey in the 4–6 mm size class occurred most commonly (80.4% of regurgitations). Compared with nestling diets of the Little Egret (Egretta garzetta) from other island heronries, nestlings of the Chinese Egret depended on prey that only occurred in coastal wetlands, whereas nestlings of the Little Egret consumed prey found in all aquatic habitats, including freshwater marshes; however, both species preyed on fish and shrimps and took prey of a similar size. The results suggest that coastal wetlands near the heronries need to be considered in habitat conservation for Chinese Egret.
... from recognizing disturbance of the water's surface caused by surface breathing fish or an escape response by fish to an approaching wading bird. Coupled with the fact that prey are easily flushed from cover by the typical egret behavior of foot-stirring, this could allow wading birds to be effective foragers in areas of dense submerged vegetation. Papakostas et al. (2005) found that Squacco Herons (Ardeola ralloides) had higher success rates foraging in open water with submerged vegetation relative to other microhabitat types, suggesting that submerged vegetation may be beneficial to foraging wading birds. In addition, birds are probably highly visible to their prey in open water habitats. Submerged macr ...
To determine how habitat structural complexity, which affects prey vulnerability, influences foraging habitat selection by wading birds, a habitat use versus availability study was conducted throughout the Florida Everglades in 2005 and 2006. Also, an experiment was conducted where structural complexity was manipulated and its effect on wading bird foraging efficiency quantified. Among-year differences in habitat selection were found, which corresponded to disparate hydrological conditions. In 2005, a poor hydrological year in terms of the seasonal recession, wading birds chose foraging sites that had less emergent vegetation, a thicker flocculent layer and higher prey density relative to random sites. In 2006, an optimal hydrological year, wading bird foraging locations were similar to random sites in all aspects. Submerged vegetation did not affect wading bird site selection in either year. The study indicated that hydrological conditions that affect prey density were more important to wading bird foraging success than fine scale variation in habitat characteristics. However, in years of poor hydrology factors that affect prey vulnerability may become increasingly important because the penalty for choosing low quality foraging habitat is greater than in years of more optimal conditions. Elucidating habitat characteristics which create high quality foraging sites will be beneficial in planning wetland restoration projects and gauging future restoration progress.
... For birds in general, mechanisms to compensate for reduced foraging efficiency include more time searching for and handling prey (Groves 1978;Burger 1980), use of different areas and foraging methods (Brandt 1984;Edwards 1989) or juveniles relying on different prey species or different prey sizes (Wunderle 1991;Papakostas et al. 2005). However, regardless of the mechanism used by juveniles to obtain sufficient amounts of food, their increased efforts imply increasing energy expenditure (Buckley and Buckley 1974;Morrison et al. 1978). ...
... We have shown that adult Great Grebes forage more efficiently than juveniles, an age-related feature common in other birds (Orians 1969; Morrison et al. 1978;Searcy 1978;Burger 1980;Schnell et al. 1983;Brandt 1984;MacLean 1986;Carl 1987;Arnqvist 1992;Papakostas et al. 2005). Foraging efficiency is supposed to increase with age and experience (Buckley and Buckley 1974;Morrison et al. 1978;Schnell et al. 1983;Brandt 1984), and foraging inefficiency of juveniles has been suggested as contributing to their higher early age mortality (Lack 1954;Ashmole 1963;Weimerskirch 2002). ...
... Edwards (1989) showed that juvenile Ospreys (Pandion haliaetus) progressively capture larger fish prey with age. Small prey captured by juveniles is a widespread feature in birds feeding upon different prey types and demonstrates the inefficiency of juveniles in capture and handling prey (Dunn 1972;Brandt 1984;Coblentz 1986;Wunderle 1991;Papakostas et al. 2005). An alternative hypothesis is that juveniles opt to capture prey of sizes with high availability while experienced adults are able to select prey of larger size. ...
The foraging and diving behavior of the Great Grebe (Podicephorus major) was studied in southern Brazil, from June to October 2005. A total of 547 dives performed by adult birds and 578 dives of juveniles were recorded. There was no age-related difference in dive duration (adults = 19.43 s; juveniles = 20.00 s) but the time elapsed between two successive dives (pause or recovery time) differed among age-classes (adults = 16.1 s; juveniles = 15.0 s). Duration of dive and pause times were weakly correlated in adults and not correlated in juveniles. Both age classes had feeding bouts of similar durations. Adults were more efficient in capturing prey (0.2 prey/min) in comparison with juveniles (0.1 prey/min) and took significantly larger prey. The main food item was the White Croaker (Micropogonias furnieri), an abundant demersal fish in the area. Juveniles had higher prey handling time in comparison with adults (78.2 s vs. 20.1 s), making them more prone than adults to being cleptoparasitized by other seabirds. Diving duration varied during daytime hours, with juveniles diving longer during early morning and late afternoon, while adults avoided foraging during midday hours. Feeding throughout the day could be a mechanism used by juvenile grebes to compensate for low foraging efficiency.
