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Male and female European Robins Erithacus rubecula display their red breasts in year‐round territorial contests. Despite the clear signalling role of the red breast, little is known about its sexual dimorphism or trends in size when Robins age. We studied these patterns in resident and migrant Robins in a Mediterranean population. Both male and female first‐year Robins had smaller red breasts than...
Carotenoid‐based plumage ornaments have the potential to signal individual condition and health in many species of birds. However, very little is known about the function of red plumage in woodpeckers. We assessed whether the red cap displayed by both male and female Middle Spotted Woodpeckers reflects individual quality, finding that the size of the cap is sex‐dependent, whereas the brightness of...
Snowy Owls Bubo scandiacus often face the sun when sitting on the ground or when perched. Such sun‐orienting has been suggested to represent a visual display to conspecifics but other explanations have not been thoroughly examined. We observed the orientation of wintering Snowy Owls to both the sun and the wind, and their perching behaviour during two winters in central Saskatchewan, Canada. We proposed...
The role and use of olfactory cues by penguins is largely under‐investigated, with only a few studies suggesting that odours are involved in prey detection, orientation and for interspecific communication. This also applies to King Penguins Aptenodytes patagonicus where little is known about their chemoreception abilities and, subsequently, the role of odours in their behavioural ecology. Here, we...
In vertebrates, the endocrine system translates environmental changes into physiological responses on which natural selection can act to regulate individual fitness and, ultimately, population dynamics. Corticosterone (CORT) and dehydroepiandrosterone (DHEA) are important regulators of the avian endocrine system but relatively few studies have investigated their downstream effects on key morphological...
The plumage of birds plays an essential role in thermal insulation and influences the heat tolerance of birds. These plumage functions are mainly determined by the number and the density of feathers, but it is unclear how feather density responds to environmental changes in wild populations. In urban birds, both high temperature and limited food could generate changes in plumage traits. To investigate...
An understanding of feather moult, an important process in the life cycle of birds, lags behind that of other avian life‐history events. This lag includes a lack of scientific attention, but surprisingly also a lack of basic knowledge regarding the moult strategy of many bird species. This situation is particularly astonishing in light of the fact that feathers are a unique characteristic of birds...
Many birds display plumage coloration and patterns that act as visual aposematic and mimetic signals for predators. Avian aposematism can also be communicated via chemical cues, where so‐called non‐host odours (NHO) emitted from the plumage, the uropygial (preen) gland or other chemical sources denote the status of birds as dangerous or unprofitable hosts for ectoparasitic and haematophagous arthropods...
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