Behavioral Responses of Captive Corvids to the Presence of Visitors

Behavioral responses of captive animals to the presence of visitors in zoos and wildlife parks can be interpreted as signs of negative (disturbance), neutral or positive (enrichment) welfare. In the present study, we investigated behavioral responses of captive common ravens, Corvus corax and crows, Corvus corone, to the presence of visitors in general and to the proximity or distance of visitors to the aviary respectively. Duration of affiliative behaviors, feeding and stress-related behaviors did not change when visitors were present compared to control situations without visitors being present. Both corvid species showed less head up behavior when visitors were in sight compared to the control condition. In contrast, preening of crows significantly increased when visitors were within two meters of the aviary compared to the control condition. The same relationship was found in regard to increase in vocalization for common ravens, but not for crows. Our results indicate that corvids, housed in a wildlife park for several years, still show behavioral responses to the presence of human visitors in close proximity to their enclosure. Overall, we did not find clear indications for reduced welfare due to visitor presence, such as increased locomotion or stress-related behaviors. We therefore conclude that the described behavioral changes are not indicative of any negative welfare impacts of visitor presence.

Bird remains from the Middle Paleolithic levels (MIS3) of Llonin Cave (Peñamellera Alta, Asturias, Spain)

Birds are abundant in fossil assemblages of Quaternary sites; they can be used in landscape recon­struction as they are well adapted to the environment. Here we present the analysis of the avian assemblage from the Middle Paleolithic levels of the Llonin Cave, where 558 bird remains have been recovered from levels G-VI and CP-VIII, belonging to at least ten different taxa: Aves indet., Galliformes indet., Lagopus lagopus Linnaeus, 1758, Tetrastes bonasia Linnaeus, 1758, Columba livia/oenas Gmelin, 1789/Linnaeus, 1758, Passeriformes indet., Alaudidae indet., Motacilla sp., Turdus sp., Corvidae indet., Garrulus glandarius Linnaeus, 1758, Pyrrhocorax sp., Pyrrhocorax pyrrhocorax Linnaeus, 1758, Pyrrhocorax graculus Linnaeus, 1766 and Corvus corax Linnaeus, 1758. This assemblage is similar to other assemblages from the Upper Pleistocene of the north of the Iberian Peninsula, and it reflects a mixed landscape, with open areas and woodland. The taphonomic analysis points to a mixed origin of the accumulation, mainly formed by medium-sized corvids dying in the cave, and also raptors accumulating their prey.

[Considerations on an alleged specimen of a Tingitan raven Corvus corax tingitanus Irby, 1874 from the Arrigoni degli Oddi Collection]

[The Common raven Corvus corax is an holoartic species, divided into 12 subspecies, three of which are present in Italy. Based on the most recent systematics, the sub-specific attribution of the Italian populations has been discussed. In the Arrigoni degli Oddi’s bird collection a specimen from Sardinia was attributed to C. c. tingitanus, a subspecies of the North Africa coasts and accidental in Italy. Some biometric parameters have been measured and compared with the literature data. This work allowed to review the attribution of this specimen by Arrigoni degli Oddi and report it to C. c. hispanus.] [Article in Italian]

Who is crying wolf? Seasonal effect on antipredator response to age-specific alarm calls in common ravens, Corvus corax

Communication about threats including those posed by the presence of predators occurs mainly through acoustic signals called alarm calls. The comprehension of these calls by receivers and their rapid antipredator response are crucial in terms of survival. However, to avoid overreaction, individuals should evaluate whether or not an antipredator response is needed by paying attention to who is calling. For instance, we could expect adults to be more experienced with predator encounters than juveniles and thus elicit stronger antipredator responses in others when alarming. Similarly, we could expect a stronger response to alarm calls when more than one individual is calling. To test these assumptions, we applied a playback experiment to wild ravens, in which we manipulated the age class (adult or juvenile) and the number (one or two) of the callers. Our results revealed a seasonal effect of age class but no effect of number of callers. Specifically, the ravens responded with stronger antipredator behaviour (vigilance posture) towards alarm calls from adults as compared to juveniles in summer and autumn, but not in spring. We discuss alternative interpretations for this unexpected seasonal pattern and argue for more studies on call-based communication in birds to understand what type of information is relevant under which conditions.