Parental behaviour of Spanish Imperial Eagles<i>Aquila adalberti</i>: sexual differences in a moderately dimorphic raptor

Margalida, Antoni; González, Luis Mariano; Sánchez, Roberto; Oria, Javier; Prada, Luis

doi:10.1080/00063650709461462

Cited by 28 publications

(23 citation statements)

References 32 publications

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“…Yet, Spanish Imperial Eagles' largest distances from the nest were registered for males during the breeding season, which concurs more with their role as food providers during this period (Margalida et al 2007a).…”

Section: Discussionmentioning

confidence: 75%

“…Kernels were fixed and least squares cross validation method was not used. Previous information about the behaviour of this species suggests that they spend a great deal of time in the nest during the breeding season (Meyburg 1975, Margalida et al 2007a and certainly both Cluster and Kernel analysis resulted in a unique and very small home range around the nest during this period. Therefore, all nest locations during BS were excluded from home range analysis to allow for comparison with the non-breeding season.…”

Section: Data Collectionmentioning

confidence: 99%

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Space Use of Adult Spanish Imperial EaglesAquila adalberti

Fernández¹,

Oria²,

Sánchez³

et al. 2009

Acta Ornithologica

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Abstract.The ranges and space use of eight radio-tracked Spanish Imperial Eagles are described. The annual mean range was 25 146 ha during the breeding season (BS) and 20 557 ha in the non-breeding season (NBS). The eagles were found up to 35.9 km away from their nest during BS and nearly 62 km away during NBS. The maximum total distance covered in one day was 113.6 km, with males flying longer distances than females during BS. There was less overlap between ranges during BS, and the mean home range varied from 3881 ha in BS to 2085 ha in NBS. The areas where territorial behaviour (display flights, defence and/or aggression) was observed contained the nest-tree, the most frequently used perches, and the feeding ground nearest to the nest. Breeding home ranges were negatively correlated with densities of Rabbits Oryctolagus cuniculus. Breeding eagles whose home range had low rabbit densities travelled 16.2-28.9 km from their nest to reach distant, undefended feeding grounds with much higher rabbit densities. Our results suggest that home ranges varied with prey density and a bird's reproductive status. Larger breeding ranges are probably related to an increase in energy requirements, while habitat quality is probably a regulatory mechanism of space use. In terms of home range analysis methodology, our observations of eagle behaviour favour Cluster Analysis over Kernel, particularly for defining distant feeding grounds.

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Section: Discussionmentioning

confidence: 75%

Section: Data Collectionmentioning

confidence: 99%

Space Use of Adult Spanish Imperial EaglesAquila adalberti

Fernández¹,

Oria²,

Sánchez³

et al. 2009

Acta Ornithologica

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“…For some vertebrate facultative predators, such as raptors, the importance and ecological influence of scavenging has largely been underestimated (DeVault & Rhodes, ; DeVault et al., ; Sánchez‐Zapata et al., 2010). This is due to the inherent biases of methods used to assess the diet of raptor species, which generally underestimate the presence of carrion and other less conspicuous remains that are difficult to identify (Redpath, Clarke, Madders, & Thirgood, ; Margalida, González, et al., ; Margalida, Sánchez, González, Oria, & Prada, ; Sánchez, Margalida, González, & Oria, ). However, several studies have revealed that scavenging is more prevalent than traditional theory implies (Beasley, Olson, & DeVault, ; DeVault et al., ; Hammerschlag et al., ; Wilson & Wolkovich, ).…”

Section: Introductionmentioning

confidence: 99%

“…In a recent study, which analyzed the size and selection of hunting zones exploited by the species to obtain feeding resources (Fernández, Oria, Sánchez, González, & Margalida, ), no additional information was obtained about differences in age classes in hunting techniques or prey selection. Indirectly, it has been documented that the presence of nonadult individuals in breeding pairs implies a lower breeding output (Margalida et al., ) and that habitat quality influences breeding success (Margalida, González, et al., ; Margalida, Sánchez, et al., ; Margalida et al., ). Males assume hunting responsibilities and are the main providers of food to the nest, as their smaller body size and other adaptations give them greater agility and maneuverability to improve hunting success (Margalida, Sánchez, et al., ).…”

Section: Introductionmentioning

confidence: 99%

“…Indirectly, it has been documented that the presence of nonadult individuals in breeding pairs implies a lower breeding output (Margalida et al., ) and that habitat quality influences breeding success (Margalida, González, et al., ; Margalida, Sánchez, et al., ; Margalida et al., ). Males assume hunting responsibilities and are the main providers of food to the nest, as their smaller body size and other adaptations give them greater agility and maneuverability to improve hunting success (Margalida, Sánchez, et al., ). In addition, supplementary feeding for the species (i.e., dead rabbits provided near nesting sites) is a management tool that demonstrates that the species can consume carrion regularly, increasing through this technique breeding success, mainly in low quality territories and pairs including inexperienced (i.e., subadult) individuals (González, Margalida, Oria, & Sánchez, ; González, Oria, et al., ).…”

Section: Introductionmentioning

confidence: 99%

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Behavioral evidence of hunting and foraging techniques by a top predator suggests the importance of scavenging for preadults

Margalida

Colomer

Sánchez³

et al. 2017

Ecology and Evolution

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Scavenging may be a regular feeding behavior for some facultative raptor species occupying low quality habitats and/or with little experience in hunting techniques. However, its importance has been largely underestimated due to methodological limitations in identifying the real proportion in the diet. Here, through direct observations, we assessed the hunting and foraging success of the threatened Spanish imperial eagle Aquila adalberti determining the influence of age, sex, breeding status, habitat quality, prey type, and landscape characteristics. From 465 observations, Spanish imperial eagles used hunting in flight (42%), scavenging (30%), hunting from a perch (16%) and kleptoparasitism (12%). Our model suggests that Prey size and Prey type best explain hunting success, followed by Landscape and Sex. Our findings suggest that Spanish imperial eagles increase hunting success with age, with scavenging and kleptoparasitism regularly used as juveniles. The absence of relationships with any of the variables considered suggests that kleptoparasitism is an opportunistic behavior used sporadically. Scavenging is also independent of habitat quality and landscape characteristics. Accordingly, low prey density is not a driver of carrion use for preadult individuals, suggesting that a lack of hunting ability obliges this age‐class to use this alternative feeding technique regularly. As a result, the threatened Spanish imperial eagle population is also prone to mortality related to the illegal use of poison baits and, potentially, veterinary drugs (i.e., diclofenac).

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Moderate evidence for the sex‐dependent effect of poisoning on adult survival in a long‐lived raptor species

Zsinka,

Pásztory‐Kovács,

Kövér

et al. 2024

Ecology and Evolution

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Survival rate is usually the greatest contributor to population growth in long‐lived species, and its accurate estimation along with the evaluation of the factors influencing it is therefore essential for effective conservation. Here, we studied the survival of breeding eastern imperial eagles Aquila heliaca in Hungary between 2011 and 2022 and investigated the effect of poisoning, the leading known anthropogenic cause of mortality. We used the Cormack‐Jolly‐Seber mark‐recapture model to estimate annual apparent survival and encounter probabilities based on the capture histories of 208 males and 411 females. We obtained encounter data from the DNA profiles of shed feathers collected at the nest sites, which we also supplemented with presences inferred from parentage analysis. The most supported model estimated a constant 91.6% annual survival over the study period, but models including the effect of sex and poisoning rate on survival had similar support. Sex difference in survival was less than 1% on average, but the survival of males decreased more with poisoning rate than the survival of females. However, due to smaller encounter probabilities, the estimates for males were less precise compared to females. Males may be more at risk from poisoning than females not only due to their more active foraging behaviour during incubation and chick‐rearing but also due to their smaller body size. Apart from providing direct practical information for the conservation management of imperial eagles, our results also highlight the importance of long‐term studies for estimating population parameters of birds of prey.

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Parental behaviour of Spanish Imperial EaglesAquila adalberti: sexual differences in a moderately dimorphic raptor

Cited by 28 publications

References 32 publications

Space Use of Adult Spanish Imperial EaglesAquila adalberti

Space Use of Adult Spanish Imperial EaglesAquila adalberti

Behavioral evidence of hunting and foraging techniques by a top predator suggests the importance of scavenging for preadults

Moderate evidence for the sex‐dependent effect of poisoning on adult survival in a long‐lived raptor species

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