Unicoloured Jay

Aphelocoma unicolor

Please send me photos and information on this species so that I can build up a more detailed database.

Madge and Burn list 5 subspecies: A. u. unicolor of Chiapas (Mexico) and Guatemala; A. u. concolor of Veracruz in Mexico; A. u. griscomi of El Salvador and West Honduras; A. u. oaxacae of Oaxaca; and A. u. guerrensis from Guerrero in Mexico. Others have also been discussed (eg by Dickey and van Rossem). Monroe refers to a number of specimens that were collected in Honduras and discusses the geographical variation within the species.

Webber and Brown (1994) made the only major study of the natural history of this species. Their study was done in an area of predominantly pine oak forest in Chiapas in Mexico, near to the Guatemalan border. This species is also found in deciduous cloud forest, where it has never been studied in detail. They made detailed observations almost every day from 10th January until the 1st June, which covered most of the breeding season. Much of their work was concerned with social behaviour within groups, which they compared to other Aphelocoma Jays.

Groups of adult (ie one year or older) birds ranged in size from 4 to 9 individuals and contained both males and females. The groups remained fairly constant throughout their observations. The territory of one group was fully mapped and had an area of 41 to 45 hectares; others were estimated to be of a similar order of magnitude. Territory boundaries were defended against neighbouring groups.

The birds ate blackberries, the fruit of wax myrtle, pine seeds and also animals such as katydids, anoles, crickets, cicadas and a nestling hummingbird. They were often seen attacking nests of the moth Hylesia frigida. Some human waste was also eaten, such as discarded corn kernels, tortillas and pastry. They mention that in previous years they had observed jays harvesting and eating acorns in July, though it was not seen throughout their main study period because they had not ripened. They discus the foraging strategies of mostly feeding on the upper sides of branches, but, when necessary, dangling beneath a branch or taking food from thin branches whilst in flight. They also discuss how they feed at Bromeliads.

The jays were observed roosting separately about 25m apart near to the top of pine trees that were about 15m in height (even if higher trees were present). They went to roost about 10 minutes or so before sundown. A table is presented, giving interactions with other vertebrates which they mobbed or which mobbed them, with those species that made the jays give an alarm call or hide etc. There are also some species that were seen to associate with groups of jays to forage.

Although most groups had more than one female and in some groups more than one of them copulated, the authors had no evidence that there was more than one nest per group. Most copulations were made by what they termed the ‘primary male’, which defended the females from other males in the group. However, these subordinate males were seen to copulate and it was possible that they may have fathered some of the young. Those males that were most likely to have fathered the young were the ones that gave most attention to the chicks. They built their nests 5.5-13.5m from the ground in trees 6-20m high. The one nest that they handled was 40cm in outside diameter and about 15cm deep. The inner cup was 11cm in diameter with a lining of lichen (Usnea) about 3cm deep with a few pine needles. All of the successful nests that they studied were in oaks, with oak forming the main material of the nest. They observed the jays building three nests in pine trees, but none of them were completed. Nest-building was first observed on January 19th. This nest was complete and the lining was being added by the 26th January. A number of individuals within the group would bring nesting material, though at all nests the breeding female brought the most. Only the breeding females laid and incubated the eggs and nestlings. All group members are thought to have shared in the feeding of the incubating female. They did not have the opportunity to check inside the nests, but there were 4 nestlings in one nest, three nestlings in two other nests and at least two in another nest. All group members were thought to have shared in the feeding of the young. Of five nests that they observed, only two were successful. Eggs were estimated to have hatched in one group on 13th March and in another on 11th March. They then fledged about 22 days later.

Biblioteca de Sonidas Aves de Mexico has a recording of call www.ecologia.edu
Infonatura has a range map www.natureserve.org
Instituto Nacional de Ecologia has an info page which includes a painting www.ine.gob.mx



Known sites

Guatemala
Aguas Amargas
Biotopo del Quetzal

Honduras
Celaque
La Muralla

El Salvador

Monroe, B. L., Jr (1968). A distributional survey of the birds of Honduras. Ornithological Monographs No. 7. AOU.

Webber, T. and Brown, J. L. (1994) Natural history of the Unicolored Jay in Chiapas, Mexico. Proc. West. Found. Vert. Zool. 5(2):135-160.