Piebald songbird (Mniotilta varia).
Dennis Church / Flickr
Males and females of piebald songbirds, North American songbirds of the arboreal family, winter in the same places, but feed on different layers of vegetation. A study in Jamaica showed that females mainly seek insects in the underbrush, while males search for insects in the middle and upper parts of the crowns, where food is more abundant and available. As noted in the article for the magazine The aukit is most likely that larger and more aggressive males simply push females out of the best foraging grounds, which negatively affects their physical condition.
During migrations and wintering, males and females of some migratory birds keep apart. For example, male red hummingbirds (Selasphorus rufus), go south earlier than females and fly east of them. It is assumed that this separation allows members of different sexes not to compete with each other for flower nectar. In other species, for example, redstart woodworms (Setophaga ruticilla), males and females winter in the same areas, but choose different habitats. Scientists do not yet know how such segregation is achieved: either it is associated with innate preferences, or larger and stronger males simply displace females from the best areas for finding food (perhaps both assumptions are partially true).
A team of bird watchers led by Nathan W Cooper of the Smithsonian Conservation Biology Institute decided to look into this issue using the example of piebald singers (Mniotilta varia) (alternative Russian name - pikukhovaya arboretum). These insectivorous passerine birds from the arboreal family (Parulidae) nest in forests in the north and east of North America, and winter in Florida, the Caribbean, and in Central and North South America.
From 2008 to 2017, researchers observed the behavior of piebald songbirds wintering in bush and mangrove forests in southern Jamaica. They annually caught birds with the help of nets, determined their gender and physical condition, and then, marking them with individual colored rings, released them. Then ornithologists conducted counts every few days, during which they determined the preferred feeding places of individual individuals and recorded interactions between them, for example, conflicts over territory.
In March-April 2010, the habits of the tagged singers were studied more closely. The authors tracked the movements of ten females and eleven males among bushes and nine females and nine males in a mangrove forest for four hours a day after sunrise. Bird watchers were particularly interested in foraging methods, as well as the height at which the birds stayed. In 2009-2010, researchers also estimated how territorial piebald songbirds are in winter. To do this, they played the voices of their relatives and assessed the reaction.
Over the years, Cooper and his colleagues have caught significantly more piebald singers among the bush than in the mangrove forest (236 individuals versus 154 individuals). At the same time, no significant differences in the choice of habitats between males and females were found. Interestingly, the territory of the females was more extensive, both in the bushes and in the forest, but they did not try to defend them when they heard the voices of their relatives, lost by scientists. In contrast, 83 percent of the males who heard the tapes aggressively attacked the alleged invader.
Observing the feeding behavior of birds, the authors found that male and female songbirds catch insects at different heights. And in shrub thickets and in the mangrove forest, most of the females searched for food in the undergrowth and, less often, in the middle part of the crowns (they almost did not appear in the upper part of the crowns). In the upper and middle parts of the crowns, males hunted much more often.
Apparently, it is more difficult for piebald singers to find high quality food in the lower layers of vegetation. This is indicated by the fact that the captured females, who mainly fed here, weighed less than males and were in worse physical shape (in addition, the condition of individuals of both sexes in the mangrove thickets was better than that of their relatives among the shrubs). At the same time, the males felt much better - probably due to access to more abundant, affordable and high-quality food.
It is not yet completely clear whether high-altitude segregation in singers is congenital or whether males displace females from the upper and middle parts of the crowns. There are several arguments in favor of the second hypothesis. Male piebald singers are larger than females and are much more aggressive in protecting feeding areas, in addition, the researchers recorded ten cases when males chased females from their territory, but not a single case when females chased males away. Consistent with the idea of male dominance is the fact that they maintained their best physical shape throughout the winter. However, the authors admit that additional research is needed to finally confirm this hypothesis, for example, experiments to remove males from certain areas.
The hooded Wilsonians, related to piebald singers (Setophaga citrina) the conflict between the sexes begins even during the rearing of the offspring. In this species, males molt two weeks earlier than females, and for this sometimes they even abandon nests with chicks. However, recent research has shown that females do an excellent job of feeding their chicks alone.
The length of the body is 14 cm, weight 11 g. The plumage of the upper part of the body is black and white, the lower part of the body is white with black stripes on the chest and on the sides.
Nesting areas are located in mixed forests in the east and north of North America, from southern Canada to Florida. In winter, birds migrate to Central and South America. A stray species in Western Europe (Ireland and Great Britain).