Biology
Influence of Habitat on Demography of Blue Jays
Blue Jays (Fig. 1) are abundant and common habitat
generalists of eastern North America. I have been
studying one or another aspect of Blue Jay biology
since the late 1980s.
Most recently, Mary Garvin and I have been
examining the role of Blue Jays as reservoir and
amplification hosts of West Nile virus and eastern
equine encephalitis virus. In collaboration with
Fig 1. Blue Jay from Florida
members of the Ohio Department of Health, we
found that West Nile viral infections in Ohio Blue
Jays soared from 3% in May to over 90% by August during summer 2002 (Fig. 2). Infection rate
did not vary with age of the birds, leading us to think that the virus did not overwinter in adult Blue
Jays during the winter of 2001-2002. Some people have speculated that the viral cycle may be
reinitiated each year when mosquitoes feed on infected corvids (the family of birds including crows
and jays) or other bird species in spring. Based on our data, it seems that the virus must overwinter
in some other host. In another study we did in Florida, we found that Blue Jays infected with eastern
equine encephalitis have lower survival rates than uninfected jays. Survival of sympatric Florida
Scrub-Jays, however, seemed unaffected by the virus. This difference between two closely related
species is unexpected and needs further attention.
http://www.oberlin.edu/biology/faculty/tarvin/bluejay.html (1 of 3)10/21/2008 10:35:17 AM
Biology
Fig 2. Increase in proportaion of Ohio Blue Jay carcasses infected with
West Nile Virus during summer 2002.
For the past several years, I have
been examining the influence of
habitat features on reproduction,
survival, and dispersal in a
population of Blue Jays. Blue Jay
density and reproductive output
are strongly related to habitat type
(Fig. 3), and adult survival and
juvenile dispersal also vary across
habitats. Variation in these habitatspecific demographic parameters
is sufficient to give rise to sourcesink population dynamics. Even
so, unlike closely related Florida
Scrub-Jays, Mexican Jays, and
Pinyon Jays, juvenile Blue Jays
have a high probability of
obtaining space in habitat that is of
sufficient quality for breeding, and
virtually all disperse within a few
months of hatching. As a
consequence, the social
organization of Blue Jays is vastly Fig 3. Variation in probability of Blue Jay nest success across
habitat types in central Florida.
different from that of closely
related, cooperatively breeding relatives. Patterns of dominance behavior in Blue Jays also differ
from the other species. This interspecific variation in dominance among New World jay species
appears to be directly related to differences in social structure, which in turn appear to stem from
http://www.oberlin.edu/biology/faculty/tarvin/bluejay.html (2 of 3)10/21/2008 10:35:17 AM
Biology
demographic differences related to habitat use. Thus, my work on Blue Jay demography and
behavior helps to understand complex population dynamics of generalist species, as well as social
evolution in the New World jays, a group of closely related species that exhibits extensive variation
in both social organization and habitat use.
home | contact biology department | oberlin online
Science Center K123
119 Woodland Street
Oberlin OH, 44074-1097
440 775-8315
FAX: 440 775-8960
site design michel dedeo
http://www.oberlin.edu/biology/faculty/tarvin/bluejay.html (3 of 3)10/21/2008 10:35:17 AM