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The role of woodpeckers (family: Picidae) as ecosystem engineers in urban parks: a case study in the city of Madrid (Spain)

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Many species of the family Picidae, such as the woodpeckers, excavate the tree-cavities where they nest. Frequently the cavities are used during a single breeding season and subsequently abandoned, which allows their use by non-excavator species for nesting or roosting. Here we analyze the role of woodpeckers as providers of nesting and refuge places in two urban parks in the city of Madrid. The environmental characteristics of the woodpecker nest-sites were also studied. Prior to the breeding season 75 trees bearing woodpecker-excavated cavities and 142 control trees (i.e. without woodpecker cavities) were located, georeferenced and characterized by a set of variables relative to the tree and its environment. During the breeding season the cavities were monitored with an endoscopic camera to verify occupation and user identity. Additionally, 71 non-excavated tree-cavities were monitored to measure their occupancy and make comparisons with those excavated by woodpeckers. Woodpeckers showed a strong preference for trees of the genus Populus: 54 of 75 (72%) woodpecker-cavities were in poplars, which comprised only 7–10% of available trees. The excavated cavities were found mainly in the trunk of the trees, north oriented and away from paths. The occupancy rate by bird species was higher, although not significantly, for excavated cavities than for natural cavities (36.0% and 23.9% respectively). The richness and composition of cavity-user species also differed between types of tree-cavities. This work shows the importance of woodpeckers as providers of nesting and refuge places for other cavity-user birds and highlights their role as ecosystem engineers in urban parks. Finally, we consider that these results can guide biodiversity conservation efforts in urban planning.
The role of woodpeckers (family: Picidae) as ecosystem engineers
in urban parks: a case study in the city of Madrid (Spain)
Patricia Catalina-Allueva
&Carlos A. Martín
Accepted: 14 December 2020
#The Author(s), under exclusive licence to Springer Science+Business Media, LLC part of Springer Nature 2021
Many species of the family Picidae, such as the woodpeckers, excavate the tree-cavities where they nest. Frequently the cavities
are used during a single breeding season and subsequently abandoned, which allows their use by non-excavator species for
nesting or roosting. Here we analyze the role of woodpeckers as providers of nesting and refuge places in two urban parks in the
city of Madrid. The environmental characteristics of the woodpecker nest-sites were also studied. Prior to the breeding season 75
trees bearing woodpecker-excavated cavities and 142 control trees (i.e. without woodpecker cavities) were located,
georeferenced and characterized by a set of variables relative to the tree and its environment. During the breeding season the
cavities were monitored with an endoscopic camera to verify occupation and user identity. Additionally, 71 non-excavated tree-
cavities were monitored to measuretheir occupancy and make comparisons with those excavated by woodpeckers. Woodpeckers
showed a strong preference for trees of the genus Populus: 54 of 75 (72%) woodpecker-cavities were in poplars, which
comprised only 710% of available trees. The excavated cavities were found mainly in the trunk of the trees, north oriented
and away from paths. The occupancy rate by bird species was higher, although not significantly, for excavated cavities than for
natural cavities (36.0% and 23.9% respectively). The richness and composition of cavity-user species also differed between types
of tree-cavities. This work shows the importance of woodpeckers as providers of nesting and refuge places for other cavity-user
birds and highlights their role as ecosystem engineers in urban parks. Finally, we consider that these results can guide biodiversity
conservation efforts in urban planning.
Keywords Cavity-nesting .Endoscopic camera .Excavator species .Keystone species .Nest-site selection .Secondary cavity
In ecosystems there are species that show a great influence on
ecological processes, affecting a large number of both animal
and plant species and the interactions that occur between
them. These species are called keystone species because they
play a fundamental role, above their abundance or biomass, in
the maintenance of the ecological system to which they be-
long (Paine 1969; Mills et al. 1993; Tellería 2012). Frequently
keystone species are also ecosystem engineers as they physi-
cally modify or create habitat characteristics and provide crit-
ical ecological resources for other species, thereby affecting
their presence and abundance (Jones et al. 1994;Wrightand
Jones 2002).
Woodpeckers (family Picidae) are considered keystone
species and ecosystem engineers because with their excava-
tion activities, they create a variety of potential niches for
other organisms (Daily et al. 1993; Jones et al. 1994; Floyd
and Martin 2016). Thus, cavities excavated by woodpeckers
are used by other bird species, mammals and invertebrates for
nesting, resting or sheltering from predators or inclement
weather (Wiebe 2006; Aitken and Martin 2007; Myczko
et al. 2016). Additionally, through their excavation activities
associated with nesting and foraging, woodpeckers accelerate
decomposition cycles of forests, increasing the recycling of
nutrients, facilitating the dispersion of wood-decaying fungi
and intervening in the control of insects (Winkler et al. 1995;
Farris et al. 2004;Faytetal.2005; Drapeau et al. 2009).
*Patricia Catalina-Allueva
Carlos A. Martín
Departamento de Biodiversidad, Ecología y Evolución, Universidad
Complutense de Madrid, C/ José Antonio Novais, 12,
28040 Madrid, Spain
/ Published online: 3 January 2021
Urban Ecosystems (2021) 24:863–871
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... For the first level of study, two buffers were created around each new nest: one with a radius of 100 m, which would represent the habitat selected to place the nest; and another with a radius of 1000 m, which would represent the available habitat. In both cases, the percentage of surface occupied by tree masses (nesting habitat) and open habitat (feeding areas) was calculated from the information For the second level of study, the following data were taken from the nest tree: tree species, height of tree and nest, diameter at breast height (hereafter, DBH), tree state (living tree, tree with dead branches, and dead tree) and presence of fungi (Melletti and Penteriani 2003;Kosinski and Kempa 2007;Urkijo-Letona et al. 2020;Catalina-Allueva and Martín 2021). This last parameter was developed by visual examination of the external fruiting bodies (Urkijo-Letona et al. 2020). ...
... The same parameters were recorded in four other trees of the wood stand that were used to represent the tree availability in those sectors actually used by woodpeckers for nesting (Melletti and Penteriani 2003;Catalina-Allueva and Martín 2021). The choice of these trees was carried out according to the following criteria: DBH of more than 30 cm (Touihri et al. 2015), distance of approximately 15 m from the tree that has the nest and oriented to the north, south, east and west, respectively (Urkijo-Letona et al. 2020). ...
The Iberian Green Woodpecker is an endemic species of the Iberian Peninsula that has been little studied. We describe the nesting habitat selection of this species in the three biogeographic regions where the species is located. The characteristics of 78 trees with occupied nests and 312 other randomly chosen trees in the vicinity of the nests were compared, as well as the proportion of open and forest habitat in two buffers (100 and 1000 m) around the nest. Nesting was confirmed in 19 different species of trees, with a mean diameter at breast height of 41.10 cm (range 30–60 cm) and a mean height of 12.43 m (range 3–20 m). Differences were found between the three biogeographic regions regarding the use of open and forest habitats and the selection of the type of tree to nest. Even so, it can be concluded that this woodpecker prefers to nest in Populus and Fagus trees, dead or at least decaying, with the presence of fungi and with a DBH greater than that of the surrounding trees. These results show not only the great plasticity of this species, but also its dependence on the existence of decaying trees and of certain dimensions in which to build the nest.
... Furthermore, in areas with many small non-native trees and tree plantations such as the one here in consideration there is a lack of natural tree cavities (Lindenmayer & Franklin 2002, Hartley 2002, Remm & Lõhmus 2011. Therefore, the role of the Great Spotted Woodpecker as ecosystem engineer could be essential for the conservation of secondary-cavity nesters and other forest species that rely on the holes excavated by it (Hardin et al. 2021, Catalina-Allueva & Martín 2021. ...
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Woodpeckers have a strong affinity to forests and woodlands, even though they can also occur in man-made environments such as tree plantations, where they assume the role of keystone species thanks to their ability to create cavities, used as nests or refuges by other animals. However, it remains unclear how the spreading of man-made environments influences the occurrence and distribution of local populations. This study aimed to investigate the macrohabitat and microhabitat selection of the Great Spotted Woodpecker during the breeding season in a protected area in northern Italy, focusing on plantations and woodland habitats. We additionally provided some data on breeding biology and estimated the density in this area. As macrohabitat characteristics, we compared the cover of woodlands (three types: oak, black locust, and willow woodlands) and tree plantations (two types: poplar plantations and reforestations). To define the microhabitat selection, we compared environmental variables around nesting sites and around an equal number of random locations in their proximity. The Great Spotted Woodpecker selected oak and black locust woodlands, but also reforestation and poplar plantations. The results of the microhabitat analysis showed that for breeding, Great Spotted Woodpeckers require food resources, but also a rather dense arboreal vegetation and large trees. We estimated a density of 7.61 ind./km 2 ± 1,13 (ES), indicating a good state of conservation. In conclusion, the Great Spotted Woodpecker occurs in both natural woodlands, where it also selects the non-native black locust, and tree plantations, despite the latter possibly being used only for foraging. Even though it is a generalist species, the woodpecker may play an important role as ecosystem engineer in both tree plantations and black locust woodlands, due to the scarcity of natural cavity in these habitats. To favour the presence of the species it is advisable to (1) increase the surface of tree vegetation of any type, (2) favour the maintenance of mature trees, (3) avoid silvicultural interventions during the breeding season (late January-late July).
... Urban wildlife plays a number of valuable roles in the continued success of urban ecosystem functions, including flower and crop pollination [8], pest control through predation [9,10], serving as a prey source, and accelerating tree-cavity production to the benefit of habitat creation [11]. Human-wildlife interactions can also benefit humans directly through betterment of mental health and developing emotional connections with the environment [12,13]. ...
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Urbanization is causing fragmentation of natural areas and impacting urban wildlife populations. Sustainability of wildlife and their habitat in arboriculture has focused on three key areas: retaining wildlife snags and beneficial-tree features (e.g., hollows/cavities), education of arborists and the public, and the adoption of systems-level thinking into arboriculture (i.e., the consideration of wildlife in risk matrices and pruning objectives). We surveyed 805 arborists using an international online survey to examine how arborists perceive these key areas of wildlife conservation and sustainability in urban forest management. Systems-level thinking was the highest rated method for arborists to support urban wildlife, followed by the retaining of wildlife snags. Education and the involvement of conservation groups received lower ratings, and the retainment of branches with hollows or cavities received the lowest ratings. In selecting important factors for wildlife snag retainment, arborists were most concerned with tree risk and targets, followed by setting (urban versus rural) and use of the tree by wildlife. Other factors that are the concern of urban ecologists were less important to respondents. Our findings support continued urban ecology education for arborists which focuses on whole/complex systems thinking to develop sustainable urban forest management practices which benefit urban wildlife.
... Technological advances, specifically the ultra-small video cameras used in inexpensive (ca. $US 100) modern borescopes now make it possible to record such data (e.g., Catalina-Allueva and Martín, 2021;Griffiths et al., 2017;Silva-Santos et al., 2012). With further miniaturization, network technology may also provide similar behavioral data in the future (Ripperger et al., 2020). ...
1 Thermal refuges are widely used by animals of all taxonomic groups and are critical to survival in severe weather. 2 Human activities are reducing the availability of natural refuges; consequently, artificial refuges are used as conservation management tools, particularly for bats. 3 Published box evaluations are generally incomplete, omitting thermal physiology and relevant thermal properties. 4 Here, we compare methods for evaluating the potential utility of bat box designs for bats and present a graphical spatiotemporal method that provides more complete information. 5 For illustration, we compare the original to 3 modified versions of the “rocket box” style bat box. 6 Box internal temperatures and generalized thermal physiology models are combined in 2 suitability indices appropriate to the mother, and to pups. 7 Results revealed that daily and seasonal averages of these indices obscured important processes and showed insignificant differences among bat box design modifications. 8 In contrast, graphical analysis highlighted the presence and spatiotemporal structure of significant differences among boxes, which were most evident in sunny weather. 9 Differences among boxes were sensitive to assumptions about bat thermal physiology and behavior. 10 We found that an external water jacket mitigated temperature extremes and extended favorable temperatures into the night, which could enhance pup development while the mothers foraged. 11 Further experiments are needed to evaluate the relation between metabolic heating by box occupants and thermal conditions within bat boxes.
Abstract Ecosystem engineers strongly influence the communities in which they live by modifying habitats and altering resource availability. These biogenic changes can persist beyond the presence of the engineer, and such modifications are known as ecosystem engineering legacy effects. Although many authors recognize ecosystem engineering legacies, and some case studies quantify the effects of legacies, few general frameworks describe their causes and consequences across species or ecosystem types. Here, we synthesize evidence for ecosystem engineering legacies and describe how consideration of key traits of engineers improves understanding of which engineers are likely to leave persistent biogenic modifications. Our review demonstrates that engineering legacies are ubiquitous, with substantial effects on individuals, communities, and ecosystem processes. Attributes that may promote the persistence of influential legacies relate to an engineer's traits, including its body size, lifespan, and living strategy (individual, conspecific group, or collection of multiple co‐occurring species). Additional lines of inquiry, such as how the recipients respond (e.g., density or richness) or the mechanism of engineering (e.g., burrowing or structure building), should be included in future ecosystem engineering legacy research. Understanding patterns of these persistent effects of ecosystem engineers and evaluating the consequences of losing them is an important area of research needed for understanding long‐term ecological responses to global change and biodiversity loss.
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Neste capítulo apresentamos os Líquens como bioindicadores no controle da poluição atmosférica. Inicialmente, descrevemos brevemente o que é poluição, bem como a legislação que a regulamenta. Em seguida conceituamos os bioindicadores e sua classificação. Trazemos, na parte metodológica, a descrição de nosso estudo. Como resultado da pesquisa, apresentamos os principais grupos de líquens utilizados como bioindicadores. Por fim, apontamos alguns espécimes existentes no litoral do Paraná como potenciais sentinelas de poluição
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Nas baixadas litorâneas atingidas pelas influências das marés, encontramos os manguezais, que são considerados regiões estuarinas e estabilizadores de baixios. Contudo exibem alterações de profundidades decorrentes, principalmente, de intervenções antrópicas provocadas pelo acelerado processo de urbanização.Sendo assim estudar os principais fatores que causam os constantes alagamentos é de grande relevância para que possamos compreender e identificar os problemas gerados em regiões estuarinas.O território de escolha foi o Bairro Ponta do Caju, no município de Paranaguá, PR. Local onde a urbanização ocorreu com a destruição dos manguezais e restingas. Relatos históricos dão conta de que esse processo teve início a partir da década de 1980, com as migrações de habitantes de comunidades pesqueiras e rurais para área urbana, principalmente da comunidade de Medeiros Município de Guaraqueçaba.A pesquisa de campo consistiu em identificar os locais que ocorrem os alagamentos no bairro Ponta do Caju. Fez-se um acompanhamento periódico entre janeiro de 2007 e dezembro de 2019, para observar a influência das marés no nível do lençol freático, e determinar o nível de saturação do lençol.Pode-se afirmar que todas às perdas ocorridas nos tipos de cobertura vegetal estão associadas à antropização. Na área de estudo, a vegetação foi devastada em função da expansão urbana, construção de residências, edificações comerciais, mercado, clube, prédios para administração pública e centro poliesportivo.Conclui-se que, os ciclos econômicos foram responsáveis diretos pelas transformações e modificações espaciais, ou seja, pela dinâmica espacial da cidade de Paranaguá e suas imediações. Também promoveram a devastação de áreas de manguezais, localizados predominantemente nas margens do rio Itiberê (Centro Histórico) e na baía de Paranaguá, com a construção do Porto. Observou-se que nos últimos 20 anos foram destruídos na área que compreende do mercado público até a ponta do caju em média 1700 m lineares de faixa de manguezais, dando lugar aos centros esportivos, urbanização sem um planejamento e zoneamento. Com este processo de antropização várias espécies desapareceram, a reprodução das espécies marinhas ficou prejudicada em função da grande quantidade de poluentes que são lançados no rio sem tratamento. O que por consequência causa doenças, proliferação de ratos e outros predadores.
Parks as artificial non-forest tree stands that serve many useful functions for people can also act as refuges for specialised species that include, for example, cavity nesters. In 2017, (from March to end of May), using the example of 54 parks in the agricultural landscape of SE Poland, the importance of 9 basic habitat parameters was assessed (tree trunk diameter, health status of the trees, proportion of dead trees, management intensity, distance to the nearest forest, distance to a forest of >10 ha in area, park area, built-up area, area of tree cover surrounding the park), for the occurrence and richness of five cavity nesters. Rural parks serve refugia for cavity nesters in the agricultural landscape, such as Great Spotted and Syrian woodpeckers and secondary cavity nesters: European Starling, Eurasian Nuthatch and Eurasian Wryneck. The park size, as well as the presence of trees with large dimensions, were positively related to the occurrence and richness of most studied species. A small share of scattered built-up areas did not negatively affect the occurrence and richness of cavity nesters, and even positively affected the occurrence of Syrian woodpecker and Eurasian Wryneck. Only significant management intensity of the parks negatively influenced the Eurasian Wryneck occurrence, and richness of secondary cavity nesters and the whole cavity nester assemblage. The protection of parks with the characteristics listed above should also be taken into account when developing park management strategies, as such areas are important for species with greater ecological flexibility, and may support biodiversity in the agricultural landscape. The negative human impact on cavity nesters may be mitigated by the designation of ‘wild zones’ in the parks, which will save ecological valuable trees and at the same time ensure the safety of visitors.
Biodiversity in urban green areas has been widely explored in several bird studies because birds are known to be important bio-indicators. Many studies have investigated the different responses of bird communities to urbanization and land use changes in urban environments. However, there are still important knowledge gaps related to the impacts of the heterogeneity, spatial structure, and connectivity of green areas on avian diversity. Such information is needed for sustainable urban planning. In this study, we focused on the comparison of bird communities between urban parks in the heritage city of Olomouc and hardwood floodplain forests in the vicinity of the city. The results of the study indicate the high importance of urban parks for the maintenance of bird diversity even though urban parks are man-made habitats. The results highlight the importance of some native vegetation structures in urban parks (old trees, bush ecotones) for maintaining urban bird biodiversity. Some implications of the results can be widely used as a decision support tool for the management of urban green areas and for the planning of ecological networks in urban landscapes.
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Critical resources for birds nesting in cities can support populations in spite of the challenges imposed by urbanization, and the identification of such resources can shed light on how species are able to adapt to novel environments. In the case of woodpeckers, these resources also support the conservation of secondary cavity-nesters. Woodpecker nesting has been well-studied in temperate regions, including within urban areas, but in subtropical and tropical regions, less is known. Here we ask what types of trees and what habitats woodpeckers use most, and which species of woodpeckers create the most nest cavities. We recorded information from 967 woodpecker nest trees in the region surrounding Miami, Florida, USA, which contained 1864 nest cavities excavated by four woodpecker species. Palm trees were used more than all other tree categories, and royal palms (Roystonea regia) were the most-used species overall. Woodpeckers preferentially excavated palm snags in every habitat where they were available and three of the four woodpecker species used palms snags over all other categories of trees. Red-bellied Woodpeckers (Melanerpes carolinus) were the most prolific cavity excavators, creating 78.1% of holes. Remnant patches of two native forest types contained the highest densities of woodpecker nest trees. We found a higher density of nest trees in moderately-developed suburban areas than either rural, agricultural areas or in the highly-developed urban core. We consider how these results can inform conservation efforts in the developing tropics, and especially within similar urbanizing environments in the nearby Caribbean.
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Tree cavities provide shelter, nesting sites and food storage for many species of birds, mammals and insects. While tree cavities are present in a variety of habitats, most prior research focuses on forests, with fewer studies completed in urban areas. However, city parks provide some habitat, and cemeteries may also provide adequate, or even better, habitat for cavity-nesters, especially in urban areas where cavities are a limiting resource. While city park and cemetery habitats have similarities, including lawn and tree maintenance, differences in tree characteristics resulting from management practices may impact tree cavity prevalence and characteristics. Our objective was to determine if parks and cemeteries were comparable habitat types in terms of tree cavity availability. We sampled 1007 trees across 10 cemeteries and 10 large parks for excavated and natural cavities throughout Cook County, IL, USA. We found that while there was no significant difference in natural cavities per tree in parks versus cemeteries, there were 3.4 times as many woodpecker-excavated cavities per 50 trees sampled in cemeteries and there was high variance in the number of excavated cavities in cemeteries. Trees in cemeteries tended to be larger and more decayed than those in parks. Trees with cavities (natural or excavated) were generally larger and more decayed than trees without cavities. This research shows the potential for cemetery and park management to promote cavity excavators and nesters.
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Nesting in old cavities may be adaptive for birds as it may offer an advantage of earlier laying and higher fitness through more recruiting offspring. Black Woodpeckers frequently use old cavities, which gives the opportunity to test how this behavior affects the timing and the success of reproduction. In this paper, we have tested a prediction that excavating a new cavity causes a delay in breeding, and that it is linked to lower productivity. We found that in the Wielkopolski National Park (western Poland) Black Woodpeckers nested exclusively in European beeches, mainly in living trees, and most frequently in their old cavities. The median relative egg-laying date in old cavities was 5.5 days earlier than in new cavities. We did not find a difference in clutch size between old and new cavities due to its low variation in the population. The proportion of offspring surviving to the end of the nestling period was 0.812 in old cavities and 0.632 in new cavities, although this did not differ significantly. However, survivorship dropped rapidly in the hatching period, especially in new cavities. In Black Woodpecker, the number of fledglings that succeeded was best explained by a model including the age of the cavity and the relative laying date. The estimated parameters of the best ranked model revealed that the number of fledglings is affected by the age of the cavity as it was higher for old cavities than for new cavities. This study shows that nest reuse is adaptive for primary excavators as it offers time and energy savings needed for cavity excavation, and increases productivity, compared to those pairs of birds that are forced to excavate a new cavity. These data are consistent with the hypothesis that cavity excavation is energetically expensive and support the prediction of tradeoffs between nest building and different components of reproduction. Responsible forest management should consider the need to protect living beeches with old cavities, which are frequently used by Black Woodpeckers.
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The identification of effects of invasive species is challenging owing to their multifaceted impacts on native biota. Negative impacts are most often reflected in individual fitness rather than in population dynamics of native species and are less expected in low-biodiversity habitats, such as urban environments. We report the long-term effects of invasive rose-ringed parakeets on the largest known population of a threatened bat species, the greater noctule, located in an urban park. Both species share preferences for the same tree cavities for breeding. While the number of parakeet nests increased by a factor of 20 in 14 years, the number of trees occupied by noctules declined by 81%. Parakeets occupied most cavities previously used by noctules, and spatial analyses showed that noctules tried to avoid cavities close to parakeets. Parakeets were highly aggressive towards noctules, trying to occupy their cavities, often resulting in noctule death. This led to a dramatic population decline, but also an unusual aggregation of the occupied trees, probably disrupting the complex social behaviour of this bat species. These results indicate a strong impact through site displacement and killing of competitors, and highlight the need for long-term research to identify unexpected impacts that would otherwise be overlooked.
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Aim: Globally, many bird species nest in tree cavities that are either excavated or formed through decay or damage processes. We assembled an overview of all tree-cavity nesters (excavators and non-excavators) in the world, analysed their geographic distribution and listed the conservation status of all species. Location: This is a global analysis of species from every continent except for Antarctica where the lack of trees precludes the occurrence of this group. Methods: We reviewed the online version of the Handbook of the Birds of the World Alive,, and primary literature for species known to nest in tree cavities, with tree cavities defined as holes that a bird can enter such that it is not visible from the outside. We classified species by nester type (excavator or non-excavator, and obligate or facultative where possible), conservation threat status and zoogeographic region, and tested for statistical differences in species distributions across realms using chi-square tests. Results: At least 1878 species (18.1% of all bird species in the world) nest in tree cavities, of which we considered 355 to be primary excavators, 126 facultative excavators and 1357 non-excavators (we were unable to classify nesting type for 40 species). At least 338 species use cavities created by woodpeckers (Picidae), excluding reuse by woodpeckers themselves. About 13% (249 species) of tree-cavity nesters experience major threats (i.e., status of vulnerable, endangered or critically endangered). The highest richness of tree-cavity nesters is found in the Neotropical (678 species) and Oriental (453) regions, and the highest proportion of threatened species in Australasia (17%). Main conclusion: Maintenance of a continual supply of cavities, a process in which woodpeckers and the processes of decay play critical roles, is a global conservation priority as tree cavities provide important nesting sites for many bird species.
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Summarizes the current research on the interplay between urban environments and bird fauna ▶ Provides a conservation-based approach, paying special attention to issues like bird monitoring and managing of bird populations, and the incardination of the design and management of urban green spaces in urban planning policies ▶ Includes examples coming from different parts of the world in an effort to obtain a thorough perspective This book provides syntheses of ecological theories and overarching patterns of urban bird ecology that have only recently become available. The numerous habitats represented in this book ranges from rows of trees in wooded alleys, to wastelands and remnants of natural habitats encapsulated in the urban matrix. Authored by leading scientists in this emergent field, the chapters explore how the characteristics of the habitat in urban environments influence bird communities and populations at multiple levels of ecological organization and at different spatial and temporal scales, and how this information should be incorporated in urban planning to achieve an effective conservation of bird fauna in urban environments. Birds are among the most conspicuous and fascinating residents of urban neighborhoods and provide urban citizens with everyday wildlife contact all over the world. However, present urbanization trends are rapidly depleting their habitats, and thus knowledge of urban bird ecology is urgently needed if birds are to thrive in cities. The book is unique in its inclusion of examples from all continents (except Antarctica) in an effort to arrive at a more holistic perspective. Among other issues, the individual chapters address the censusing of birds in urban green spaces; the relationship between bird communities and the structure of urban green spaces; the role of exotic plant species as food sources for urban bird fauna; the influence of artificial light and pollutants on bird fauna; trends in long-term urban bird research, and transdisciplinary studies on bird sounds and their effects on humans. Several chapters investigate how our current knowledge of the ecology of urban bird fauna should be applied in order to achieve better management of urban habitats so as to achieve conservation of species or even increase species diversity. The book also provides a forward-looking summary on potential research directions. As such, it provides a valuable resource for urban ecologists, urban ecology students, landscape architects, city planners, decision makers and anyone with an interest in urban ornithology and bird conservation. Moreover, it provides a comprehensive overview for researchers in the fields of ecology and conservation of urban bird fauna.
The Black Woodpecker (Dryocopus martius L.) is both an ecosystem engineer and an umbrella species: it has the capacity to modify its environment through cavity excavation, which in turn favors a large range of species that depend on cavities but are unable to dig them themselves (secondary cavity nesters). However, the factors driving cavity excavation by the Black woodpecker at the tree scale remain poorly known. We analyzed the characteristics of trees bearing Black Woodpecker cavities to assess the bird's local habitat requirements and their conservation potential as habitat trees. We compared the traits and characteristics of trees bearing Black Woodpecker cavities (n=60) and control trees (n=56) in two managed lowland broadleave-dominated forests in France. We hypothesized that: (i) Cavity-trees would have lower wood density and display more conks of fungi than control-trees; (ii) The local environment of cavity-trees would be less crowded than those of the control trees. In particular, the first branch would be higher up, and their first neighboring tree would be further away from cavity-trees compared to control-trees; (iii) Cavity-trees would display a higher number of other woodpecker cavities and more saproxylic microhabitats than the control-trees. We validated most of our hypotheses and showed that cavity trees differed significantly from their control counterparts. Black Woodpeckers excavate trees with softer wood and higher first branches in a less crowded environment, thus minimizing both the energy dedicated to cavity excavation and predation risk. Second, cavitytrees bear more microhabitats and play a complementary umbrella role than what was documented before. They also appear a good candidate for habitat-tree conservation. In terms of biodiversity-friendly management measures, it would be beneficial to favor large isolated standing trees devoid of low branches (notably beech), especially in stands dominated by other tree species.
In forests worldwide, ∼10−40% of bird and mammal species require cavities for nesting or roosting. Although knowledge of tree cavity availability and dynamics has increased during past decades, there is a striking lack of studies from boreal Europe. We studied the density and characteristics of cavities and cavity-bearing trees in three categories of forest in a north-Swedish landscape: clearcuts with tree retention, managed old (>100 years) forest, and unmanaged old forest. Unmanaged old forests had significantly higher mean density of cavities (2.4±2.2(SD) ha⁻¹) than managed old forest (1.1±2.1 ha⁻¹). On clearcuts the mean cavity density was 0.4±2.3 ha⁻¹. Eurasian aspen (Populus tremula) had a higher probability of containing excavated cavities than other tree species. There was a greater variety of entrance hole shapes and a higher proportion of cavities with larger entrances in old forest than on clearcuts. Although studies of breeding success will be necessary to more accurately assess the impact of forest management on cavity-nesting birds, our results show reduced cavity densities in managed forest. To ensure future provision of cavities, managers should retain existing cavity-bearing trees as well as trees suitable for cavity formation, particularly aspen and dead trees.
Although many parrot species are decreasing in their native range, introduced parrot populations can be found in urban areas around the globe. We thus need to understand how they adapt to this novel environment and to assess the possibility of a range expansion that might threaten native species. We studied population growth, nest site requirements, as well as limiting factors like reproductive output and mortality of the only European population of Yellow-headed Parrots (Amazona oratrix) in the city of Stuttgart, southwest Germany, to assess the risk of a possible range expansion. Although offspring could be seen on a regular basis, parrot numbers hardly increased during the last 5 years (51 individuals in spring 2015, including 12 breeding pairs). Ten accessible nest cavities were studied in detail: they were located exclusively in large, old London Plane (Platanus × acerifolia) trees in an area of less than 1 km2 in the city’s public parks and were at least 65 cm deep. Average reproductive output was 1.3 fledglings/pair, which is high in comparison to data from birds in their native range. Mortality, especially of young parrots, appears to be high due to risks in urban areas such as collisions with vehicles and windows and could partly explain slow population growth. This slow population growth in combination with the need for sufficiently large nest cavities may hinder a range expansion of this species in future years.