Abstract
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).
Highlights
Carrion consumption is a key ecological process influencing population dynamics, community structure, and ecosystem functioning (DeVault, Rhodes, & Shivik, 2003; Selva & Fortuna, 2007)
It is necessary to assess the influence of age, habitat quality, and landscape characteristics on the frequency of scavenging in the diet of this species to know their relevance in their trophic ecology
With a generalized linear models (GLMs), we studied 50 individual kleptoparasitic interactions assessing whether Sex, Age, Landscape, Habitat, or Breeding status affected the success of kleptoparasitism
Summary
Carrion consumption is a key ecological process influencing population dynamics, community structure, and ecosystem functioning (DeVault, Rhodes, & Shivik, 2003; Selva & Fortuna, 2007). Sánchez-Zapata et al (2010), with the help of automatic cameras, identified golden eagles Aquila chrysaetos on 24 (57%) of 42 monitored carcasses, with similar presence throughout the year This suggests that the role of carrion in the feeding habits of facultative scavenger raptors may be more important than estimated. It is necessary to assess the influence of age, habitat quality, and landscape characteristics on the frequency of scavenging in the diet of this species to know their relevance in their trophic ecology Given this background, we hypothesized that immature and less experienced individuals (mainly males) can have lower success on hunting techniques and, as a result, use alternative techniques (i.e., kleptoparasitism, scavenging) to optimize foraging success. We estimate the importance of other feeding techniques (kleptoparasitism and scavenging) to obtain food resources, discussing the implications from a behavioral and conservation perspective
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