User:Fred Tremblay/sandbox

Coloniality and brain size
Individual recognition is one of the most basic form of social cognition. If we were to define individual recognition, it would imply that a given individual has the capacity to discriminate a familiar individual from another one at any given time. It is believed that in many species, group size is often a representation of social complexity, with higher social complexity demanding higher cognitive capabilities. This hypothesis is also known as the "social brain hypothesis" and has been supported by many researchers. The idea behind this hypothesis is that in order to succeed, large group size require more complex interactions. Many researches have looked at the effect of sociality on the brain development, mostly focussing on non-human primate species. In primates, it has been shown that relative brain size, when controlling for the size of the species and the phylogeny, seemed to correlated with the size of the social group. These results allowed for a direct correlation between sociality and cognition. However, when reproducing such experiments in non-primates species, such as in reptiles, birds and even other mammalian species, the correlation between brain size and social group size does not seem to exist. In birds, it has been shown that social complexity is a more reliable proxy for brain size, as it relies not only on the number of individual but also on the social interactions and all the necessary skills to live successfully in a group. Moreover, a study done on mountain chickadees looking at the impact of sociality on the hippocampus size as well as on neurogenesis found no evidence of change related to group size, therefore rejecting the "social brain hypothesis" in birds.

Role of recognition
In the wild, recognition can have many advantages. When looking at monogamous birds species, being able to recognize your mate can be crucial. As colonial birds tend to cluster in high density group, finding your mate can be a challenge. Being able to identify your mate is not all, recognition can also help in the context of mate selection as individual recognition allows to avoid inbreeding with conspecifics. It has been shown that storm petrels, a colonial seabird that nest in burrows, select their mate partially based on the relatedness of the individual so that inbreeding is avoided. In the case of storm petrels, individual relatedness is assessed based on olfactory signatures that allow them to distinguish closely related individuals from non-related ones. The capacity of an individual to identify conspecific is not only used to avoid inbreeding, but can also be used in order to help closely related individuals. Such instances can be seen in scrub jays, who's offspring stay after fledging in order to help raise the next brood.

Moreover, recognition can be useful in the context of chicks identification. Being able to recognize your own chick is essential in many colonial birds species as chicks can wander around and mix up with others' chicks. Feeding the wrong chick would end up high cost for the parent with little to no benefit for their own reproductive success. For example, in herring gulls, which are ground nesters, chicks can be found wandering around the colony only a few days after hatching from the egg. Recognition of its own chick is even more important in the case of species like herring gulls as adults will often feed on chicks of other members of the colony. Moreover, in order for recognition have evolved in the context of chick identification, recognition has to be beneficial for both the chicks and the adults. Still looking at herring gulls, being able to properly identify its own chick is beneficial for the parent for the reason given above, but it is also beneficial for the chick. Chicks will often hide when the parents are not present in order to avoid being predated on by other adult herring gulls or any other predator. Therefore, being able to recognize your parent is crucial in order to reveal your position to the right adult. In case of bird species that raise many offspring at once, chicks that are able to recognize their parents may increase their begging rate and therefore obtain more food in return.

Olfactory recognition
It has been believed for a long time that birds had a very bad sense of smell, but recent studies have demonstrated that some species of birds such as the

procellariiformes have a quite developed sense of smell. Olfaction seems to be used in an array of different task such as for finding food, migrating but also plays a role in kin recognition. In burrowing species such as in puffins, auks and petrels, smells seems to be at the basis of mate and nest recognition. The procellariiformes, also known as tubed-noses, are one of the best studied order when it comes to olfaction as they seem to have a quite developed sense of smell. A study done on storm petrels shown that not only petrels use olfaction in order to find their burrow and their mate, but that they are also aware of their own smell. Petrels nest in dense colonies and use the smell of their mate or their own smell in order to find their burrow and avoid entering the wrong burrow. Such mechanism of recognition has been shown in Auks as well as they come back to the colony at night, where vision is not a reliable sense to find your mate. When looking at the available literature, olfactory cues seems to be used mostly by colonial birds that nest in burrows with few exceptions like in bank swallows, which exhibit parent-offspring recognition but based on auditory cues.

For what concerns chick recognition in burrowing birds, Minguez (1997) showed that there was no chick recognition in storm petrels as their is no need to be able to identify your chick. One of the advantage of burrow nesting is that your chick is confined in the burrow until it is ready to fledge. Loosing your chick in a crowded colony is therefore not a risk for the parents. It is likely that chicks will acquire their "signature smell" only later upon fledging the parental nest. There are few instances of burrowing bird that have mechanism of chick recognition, but as recognition is a costly mechanism, it tend to be lost in many bird species for which it is not necessary.

Acoustic recognition
Not all bird species have a sense of smell as developed as the procellariiformes, but in many species, song is something that is quite developed. In many species of colonial birds, especially in species that do not nest in burrows, the environment in the colony tend to be quite loud and is filed with countless acoustic stimuli. Many researchers have looked into how can individuals identify each other in a such heavily charged acoustic environment. Recognition based on acoustic signatures has been demonstrated in many bird species such as in penguins, swallows , gulls , razorbills and more. A study done on king penguins by Jouventin et al. (1999) was one of the first study to look at the technicalities behind acoustic recognition. They found that chicks could identify their parents based on an acoustic signature specific to the pattern of the call as well as the frequency of the parents call. The amplitude of the call did not seem to affect the call signature. A similar study done on Black-headed gulls in 2001 obtained results supporting that the acoustic signatures of parents calls is most likely based on a redundant pattern and the frequency of the call with no effect regarding the amplitude. This study also supported that the mechanism of acoustic recognition is most likely the same in most species within Laridae, the gull family. Nevertheless, not all members of the Laridae family exhibit parent-offspring recognition. The black-legged kittiwake, a small cliff nesting gull, does not seem to recognize his chick. This lack of recognition is most likely the result of cliff nesting, as chicks cannot explore far from the nest and get mixed with other chicks. Recognition would have then been lost in kittiwakes. Other exceptions can be found, for example in razorbills. Razorbills exhibit parent-offspring recognition, but research as shown that only males and chicks exhibit such behaviour, meaning that females do not recognize their chick and vice versa. Such difference between the parents can be explained when looking at the natural history of razorbills. Like in kittiwakes, razorbills are cliff nesters, limiting the chicks movement quite a bit. However, when the chick will fledge, the male only will bring the chick out at sea and will keep caring for its chicks for a little while after fledging, creating the need to be able to recognize its own chick. As females do not follow its offspring at sea. their is no need for her to recognize her own chick.