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Nest level productivity (0–3 chicks per breeding attempt, N = 380 nests) depending on (a) the month of egg-laying (black bars on x-axis represent sample sizes); and, (b) geese interactions on nest level: no geese present, geese present, nest harassment and nest usurpation ('nest gscore' ranging from 0–3). P-values indicate significance in post-hoc comparisons. Figure based on predicted values of GLMMs, 95 % CIs in shaded grey or error bars; model details are given in Table 1
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Background: Black sparrowhawks (Accipiter melanoleucus) recently colonised the Cape Peninsula, South Africa, where the species faces competition for their nest sites from Egyptian geese (Alopochen aegyptiaca) which frequently usurp black sparrowhawk nests. In this paper, we test the hypothesis that multiple nest building by black sparrowhawks is a...
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As the world’s human population increases, transformation of natural landscapes into urban habitats continues to increase. In Africa, rates of human population growth and urbanisation are among the highest in the world, but the impacts of these processes on the continent’s biodiversity remain largely unexplored. Furthermore, the effects of ongoing...
Citations
... Dolenec (2019) found that a difference in height of at least 2 m was sufficient for great tits to distinguish between two nest boxes on the same tree whereas the distance between the entrances of our boxes on the same tree was only 33 cm. There are reports of birds beginning to construct nests in multiple sites (Berg et al. 2006; Macqueen and Ruxton 2023) but in those cited cases, the alternate nests were usually spaced well apart and were probably not the result of a confusion of the builder (Sumasgutner et al. 2016). article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. ...
Experiments since the classic studies of Niko Tinbergen have provided evidence that animals use visual landmarks to navigate. We tested whether birds use visual landmarks to relocate their nest sites by presenting two species of cavity nesting birds with a dyad of nest boxes with different white markings around the entrance, a circle or a triangle. When the two boxes were erected in close proximity on the same tree, pied flycatchers Ficedula hypoleuca and blue tits Cyanistes caeruleus confused the entrance of their nest both when the boxes had different external markings and when they were unmarked. Most females added nest material to both boxes of a dyad and one third of the flycatchers laid eggs in both boxes although a female can only incubate the eggs in one nest at a time. Thus, the birds did not use external markings around cavity entrances for orientation. We also tried to replicate a previous study purporting to show that migratory birds use social learning of the external appearance of nests from other species. However, pied flycatchers did not choose boxes with the same painted markings as those applied to nests of resident great tits Parus major which were judged to be high quality “demonstrators” from their large clutch sizes. We argue that conclusions from previous studies on social learning based on external markings as landmarks on nest cavities in birds need to be reconsidered.
... Nest site availability can be a limiting factor for birds that nest in cavities and similar structures (Newton 1998 abundance of black vultures increases across their range, it would be anticipated that competition for nest sites would increase as populations grow and suitable nesting conditions are limited. Such competition has been argued as a cause for nest destruction and usurpation among other raptors (e.g., Fernández and Donázar 1991;Sumastgutner et al. 2016;Boal 2023). ...
Black vultures (Coragyps atratus) are increasing in number and distribution. These birds rely heavily on man-made structures for nesting and are appearing to adapt to nesting within more urbanized areas. Black vultures are solitary breeders, yet gregarious with conspecifics outside of their nest sites. The sociality of these birds likely allows information on nest sites to be acquired by conspecifics. Here, we report on the first documentation of conspecific nest destruction by black vulture, an event that occurred in May–June 2022 in Mississippi, USA. This nest destruction was photographed over a 2-week period through a game camera set within the nest chamber. As black vulture populations continue to increase, and as potential nest sites for these birds may become limited, we anticipate higher incidence to conspecific nest destruction, and nest usurpation among black vulture throughout their range.
... For instance, birds will try to build/use nests or areas with reduced predation risk or nests not easily accessible to other species, including humans (Reynolds et al., 2019;Perez et al., 2023). Moreover, usurpation for already built nests or nesting sites may occur between species because of the time and energy required for nest building (Sumasgutner et al., 2016). Therefore, increased size or dominance could potentially assist in raptor species' ability to reproduce and persist in a given area, resulting in the exclusion of an inferior species. ...
... Our study aimed to establish whether there is likely to be increased potential constraints for finding nesting sites for crowned eagles (female body mass ~4.7 kg) and black sparrowhawks (Accipiter melanoleucus) (female body mass ~1.0 kg) in the urban mosaic landscape of eThekwini Municipality. Both species breed annually and generally have a single nest per territory (McPherson et al., 2016;Wreford et al., 2017), but black sparrowhawks may have several per territory (Sumasgutner et al., 2016). Similar to crowned eagles, black sparrowhawks also use mature, tall trees for nesting, with most of them being exotic tree plantations (e.g., Eucalyptus spp.), but a considerable proportion of indigenous trees are also used by both raptor species (McPherson et al., 2016;Wreford et al., 2017). ...
... Nest building is considered one of the most time-consuming activities for most avian species (Mainwaring & Hartley, 2013;Sumasgutner et al., 2016). Therefore, possible increased constraints in finding nesting sites, especially in landscapes with limited remaining natural habitat, can be detrimental to population persistence through its effect on recruitment (Hakkarainen et al., 2004). ...
... Dolenec (2019) found that a difference in height of at least 2 m was su cient for great tits to distinguish between two nest boxes on the same tree whereas the distance between the entrances of our boxes on the same tree was only 33 cm. There are reports of birds beginning to construct nests in multiple sites(Berg et al. 2006; Macqueen and Ruxton 2023) but in those cited cases, the alternate nests were usually spaced well apart and were probably not the result of a confusion of the builder(Sumasgutner et al. 2016).If birds do not use vision, they may use odors to locate their nest, which has been shown in some seabirds nesting in burrows in colonies(Léon et al. 2003;Zidat et al. 2023). There is con icting evidence whether passerines like blue tits use smell (e.g., odors of predators) at nest boxes(Amo et al. 2008(Amo et al. , 2018. ...
Experiments since the classic studies of Niko Tinbergen have provided evidence that animals use visual landmarks to navigate. We tested whether birds use visual landmarks to relocate their nest sites by presenting two species of cavity nesting birds with a dyad of nest boxes with different white markings around the entrance, a circle or a triangle. When the two boxes were erected in close proximity on the same tree, pied flycatchers Ficedula hypoleuca and blue tits Cyanistes caeruleus confused the entrance of their nest both when the boxes had different external markings and when they were unmarked. Most females added nest material to both boxes of a dyad and one third of the flycatchers laid eggs in both boxes although a female can only incubate the eggs in one nest at a time. Thus, the birds did not use external markings around cavity entrances for orientation. We also tried to replicate a previous study purporting to show that migratory birds use social learning of the external appearance of nests from other species. However, pied flycatchers did not choose boxes with the same painted markings as those applied to nests of resident great tits Parus major which were judged to be high quality "demonstrators" from their large clutch sizes. We argue that conclusions from previous studies on social learning based on external markings as landmarks on nest cavities in birds need to be reconsidered.
... Monitoring species in such habitats requires significant effort and costs, and may even require aerial surveys to find nests over large areas [27,28]. Some territorial species may also build and use alternative nests in different years [29,30], and finding these alternative nests presents another challenge to monitoring the productivity of such species. If intensive methods (e.g. ...
Traditionally, demographic monitoring of birds has been undertaken by intensive monitoring of nesting sites. However, this is challenging for low-density species, whereby the effort and costs involved in locating and monitoring remote sites can be prohibitive or even bias research findings. We show that Global Positioning System (GPS) tracking can overcome these challenges for a low-density raptor. Field monitoring of martial eagles Polemaetus bellicosus from 2013 to 2021 showed consistently poor breeding performance, with a mean productivity of 0.22 (±0.04) fledged young/pair/year. Using GPS tracking data to infer breeding performance gave a significantly higher productivity of 0.46 (±0.10) fledged young/pair/year. Breeding rate and success were also underestimated by field monitoring. These differences were likely due to logistical constraints of field monitoring, particularly relating to finding alternative nests. Comparing costs between approaches, we estimated that GPS monitoring was financially cheaper than field monitoring per sample after 10 years. Carbon costs per sample were lower for GPS-based approaches than field monitoring from the second year, and over a 10-year period GPS monitoring produced considerable savings (200% less carbon). We recommend that despite high initial costs, for long-term demographic monitoring of low-density species, or where logistical constraints make traditional field monitoring inaccurate, remote monitoring options should be considered.
... In the only focused study on the species' life history, Hamerkops were frequently usurped from nests by Barn Owls or other species so that pairs built at least three nests per year (Wilson et al. 1987). Black Sparrowhawks Accipiter melanoleucus in South Africa build multiple nests in a territory to reduce aggressive interactions with Egyptian Geese (Sumasgutner et al. 2016). Hamerkops may do the same given the attractive structure the nest provides to other birds. ...
Nest-building is an energetically expensive activity for birds. Consequently, some species opportunistically use other species’ nests. The Hamerkop Scopus umbretta, an endemic sub-Saharan African waterbird, constructs one of the largest nests of any bird in the world. Little is documented on the role of Hamerkop nests in the breeding biology of other avian species. Therefore, we assessed this from the literature and first-hand observations to determine which species use Hamerkop nests and their associated behaviours. We found at least 20 avian species using Hamerkop nests for breeding in 18 African countries. The Barn Owl Tyto alba was the most commonly reported species using Hamerkop nests. Six species actively usurp nests from Hamerkop pairs. Nine species nested inside the nest chamber, and eight nested on top of the structure. This highlights the role of Hamerkop nests in other avian species’ breeding.
... Breeding density, generalist diet, flexibility in the use of habitat and in use of native or exotic trees to nest and extension of breeding season have been cited as important strategies permitting successful reproduction of raptors in urban mosaic landscapes (Kübler et al. 2005;Sumasgutner 2013;Boggie and Mannan 2014;Kreiderits et al. 2016;Sumasgutner et al. 2016;Rose et al. 2017). However, there are cases in which these habitats are selected for nesting but reproductive output can be lower than in non-urbanized or less urbanized habitats. ...
Urban sprawl is recognized to homogenize biota, with several species that fail to adapt to these new human scenarios. However, some species can live and breed successfully in urbanized habitats. We compared the breeding performance of the relatively common raptor and poorly studied, chimango caracara (Milvago chimango) in an urban gradient of central Argentina. Breeding data of 359 nests were collected during breeding seasons from 2010 to 2012. Birds nested in colonies of 3-75 pairs. Overall breeding success was 49.9% with productivity at 1 ± 1.14 chicks per nest. Models revealed that reproductive success and productivity were higher in nests with earlier laying dates and sited in larger colonies and that urbanization gradient did not affect either reproductive output or laying day. Urban habitats in central Argentina appear to provide similar reproductive success of chimango caracara than rural or natural habitats. Thus, chimango caracara shows behavioral plasticity for their successful persistence to human changes as reflected in successfully breeding in a wide variety of habitats such as natural, rural, and urbanized environments that have been impacted by humans.
... 400 mm/year), with peaks in June and July (Cowling et al., 1996). Breeding territories are maintained between seasons, although the nesting tree may change (Sumasgutner, Millán, et al., 2016). ...
Urban areas provide breeding habitats for many species. However, animals raised in urban environments face challenges such as altered food availability and quality, pollution and pathogen assemblages. These challenges can affect physiological processes such as immune function and antioxidant defences which are important for fitness.
Here, we explore how levels of urbanisation influence innate immune function, immune response to a mimicked bacterial infection and antioxidant capacity of nestling Black Sparrowhawks Accipiter melanoleucus in South Africa. We also explore the effect of timing of breeding and rainfall on physiology since both can influence the environmental condition under which nestlings are raised. Finally, because urbanisation can influence immune function indirectly, we use path analyses to explore direct and indirect associations between urbanisation, immune function and oxidative stress.
We obtained measures of innate immunity (haptoglobin, lysis, agglutination, bactericidal capacity), indices of antioxidant capacity (total non‐enzymatic antioxidant capacity (tAOX) and total glutathione from nestlings from 2015 to 2019. In addition, in 2018 and 2019, we mimicked a bacterial infection by injecting nestlings with lipopolysaccharide and quantified their immune response.
Increased urban cover was associated with an increase in lysis and a decrease in tAOX, but not with any of the other physiological parameters. Furthermore, except for agglutination, no physiological parameters were associated with the timing of breeding. Lysis and bactericidal capacity, however, varied consistently with the annual rainfall pattern. Immune response to a mimicked a bacterial infection decreased with urban cover but not with the timing of breeding nor rainfall. Our path analyses suggested indirect associations between urban cover and some immune indices via tAOX but not via the timing of breeding.
Our results show that early‐life development in an urban environment is associated with variation in immune and antioxidant functions. The direct association between urbanisation and antioxidant capacity and their impact on immune function is likely an important factor mediating the impact of urbanisation on urban‐dwelling animals. Future studies should explore how these results are linked to fitness and whether the responses are adaptive for urban‐dwelling species.
... This behavior is adaptive because males in a certain group may have a better chance to increase reproductive success (Balshine et al., 2001;Riehl, 2012;Sherley, 1990;Stiver et al., 2013;Theuerkauf et al., 2009). In addition, males of some species build multiple nests sequentially in a reproductive season (Friedl & Klump, 2000;Sumasgutner et al., 2016). Co-breeding males displaying this behavior must allocate their reproductive effort within and among nests. ...
... For instance, males with larger nests result in higher reproductive success in birds and fishes (Barber, 2013;Bose et al., 2018;Lehtonen et al., 2007;Soler et al., 1998). Finally, males may build multiple nests across a breeding season to increase reproductive success (Friedl & Klump, 2000;Sumasgutner et al., 2016). This is a bet-hedging strategy when some nests fail to produce the young (Gross, 1996;Koenig & Walters, 2015), and co-breeding may facilitate such a strategy as individual males need not expend as much effort as constructing nests alone. ...
Nest construction is an energetically costly behavior displayed by males in many taxa. In some species, males construct nests and co‐breed with other males and they may construct multiple nests in a breeding season. However, little is understood about how allocation of effort within and among nests affects male reproductive success. We characterized reproductive effort of male bluehead chub (Nocomis leptocephalus), a nest‐building stream fish, in an entire breeding season in a small stream in South Carolina, USA. By using automated monitoring methods on 18 nests, we recorded time spent by 34 males during the spawning season in 2017. We then linked effort within and among nests to reproductive success, measured by the number of offspring assigned genetically to each male. A Bayesian hierarchical analysis showed that larger males spent more time constructing and maintaining a given nest, and consequently were more reproductively successful than smaller males on the same nest. Combined with aggressive behavior displayed by larger males toward smaller males, this finding suggested that reproductive effort, including agonistic interactions within nests was a determinant of reproductive success. In addition, larger nests constructed by more males led to higher male reproductive success, suggesting the importance of cooperative behaviors. Number of nests that males constructed, a measure of effort across nests, was not a predictor of reproductive success, further supporting that reproductive success varied among nests due to nest size. Our study showed that male reproductive success was determined by both aggressive and cooperative behaviors in a co‐breeding species.
... Through this practice, the traditional nest site experiences increased exposure to weather extremes, which potentially reduces nest success. These eucalyptus trees provide not only nesting sites for Crowned Eagles (McPherson et al., 2016a(McPherson et al., , 2021, but also Black Sparrowhawks (Accipiter melanoleucus; Malan and Robinson, 2001;Malan and Shultz, 2002;Sumasgutner et al., 2016;Wreford et al., 2017), African Fish Eagles (Haliaeetus vocifer; Welz and Jenkins, 2005), and Woolly-necked Storks (Ciconia episcopus Thabethe et al., 2021). Considering our results about the successful protection of nest trees and the multi-year nest-site fidelity in Crowned Eagles, identified nest trees should remain protected for at least 3 years after a breeding event. ...
Larger carnivores often trigger human-wildlife conflicts that arise from perceived threats to humans and domestic animals’ safety, which generate the need for management and removal strategies. These issues become especially challenging when humans and wildlife coexist close to one another, for example, in urban landscapes. African Crowned Eagles (Stephanoaetus coronatus) are powerful forest raptors that breed within the metropolitan green-space system of Durban and Pietermaritzburg, South Africa. Negative human-wildlife interactions can occur because eagles occasionally predate on pets, such as cats (Felis catus) and small dogs (Canis lupus familiaris), and provisioning domestic stock to nest sites has previously been quantified. Here, wildlife management becomes critical, usually aimed at reducing or eliminating causes of economic or social harm, but have to be balanced against conservation goals regarding threatened species. In this study, we (i) identified causes of harm or loss of Crowned Eagles because of injuries (n = 53 incidents; 31 mortalities); and (ii) describe interactions with negative perceptions to human livelihoods, particularly concerning predation on pets and livestock. Anthropogenic causes of mortality were more likely to be reported than remote natural deaths, which provides important opportunities for mitigation measures. Most avoidable are electrocution on utility poles, persecution via gunshot wounds and poisoning (targeted or secondary), while collisions with anthropogenic structures, such as glass panes, vehicles and fence wires, are more challenging to mitigate. Out of 44 verified Crowned Eagle vs. pets and livestock conflicts, we documented 19 dog attacks (2012–2020), with detrimental impacts on social perception and acceptance of urban eagles. Pet and livestock conflicts were primarily associated with juveniles and immature eagles (83%). Of these, 19% occurred during September alone, which marks the end of the post-fledging dependency period; 70% occurred outside the breeding season. We provide management recommendations regarding various categories of Crowned Eagle human-wildlife interactions. For example, activities such as rehabilitation and falconry can coordinate to achieve a high standard of public support and conservation outcomes for Crowned Eagles. Finally, we discuss using different management intervention strategies, including rehabilitation, falconry, re-wildling processes, and lethal control of specific “problem” individuals toward achieving the goal of sustainable, healthy Crowned Eagle populations that coexist with humans in urban landscapes.
