Title
Stopover biology of migratory landbirds in a heavily urbanized landscape: The New York Metropolitan Area
Author(s)
Seewagen, C.L.
Published
2010
Abstract
Migration routes of many Nearctic-Neotropical landbirds pass through the most
urbanized regions of North America. Migrants use urban habitat fragments as stopover
sites and commonly occur in cities at exceptional density. Yet, knowledge of migrant
stopover biology and refueling opportunities in such places is severely limited. This
dissertation examined several aspects of migrant stopover biology in the New York
metropolitan area to gain a more holistic understanding of how migratory landbirds
utilize urban stopover sites, and ultimately to assess the quality of urban habitats as
stopover sites. I first generated morphometric predictive models using salvaged bird
specimens to allow me in subsequent studies to noninvasively measure the energetic
condition (fat mass) of migrants in New York City (NYC). Next I compared the refueling
performance of migrants in NYC to that of conspecifics in less-disturbed forests outside
of the city. Blood plasma metabolite profiles indicated that refueling conditions for
migrants were no poorer in NYC than in the non-urban habitats. Further, migrant
refueling rates were comparable to, and in some cases higher than, those reported in the
literature for birds at various non-urban stopover sites. Measures of arthropod biomass
suggested food abundance for insectivorous migrants was also similar within and outside
NYC. I then showed that stopover refueling in NYC often involved substantial increases
in lean mass. This finding carries implications for stopover habitat management practices,
as migrants using these sites will require high-protein foods in addition to the lipid- and
carbohydrate-rich foods that maximize fattening rates. Next, radio-telemetry data from a
small pilot study provided one of the first descriptions of migrant stopover durations
within a city. Stopover durations ranged 1-14 days and were negatively related to fat
mass, but not lean body mass, upon arrival. A larger-scale telemetry study revealed that
migrant spatial behaviour in NYC was in many ways similar to what has been observed
in passerine migrants in non-urban areas. Movement patterns were indicative of an ability
to search for, locate, and occupy suitable microhabitat, and temporary home ranges
suggested forest size was more than sufficient to meet their area requirements.
Collectively, these studies provide a comprehensive assessment of the quality of urban
habitats as migratory bird stopover sites. Findings indicated that the sites examined are
functioning in the same fashion as less-disturbed, larger forest tracts elsewhere. No
evidence was found to suggest that stopover refueling conditions within one of the
world’s most urbanized landscapes are inadequate for migrating landbirds.
Access Full Text
A full-text copy of this article may be available. Please email the WCS Library to request.
Back
PUB14714