The Wilson Journal of Ornithology 124(4):698-703, 2012 
IDENTIFYING MIGRATORY PATHWAYS USED BY RUSTY 
BLACKBIRDS BREEDING IN SOUTHCENTRAL ALASKA 
JAMES A. JOHNSON, 1 6 STEVEN M. MATSUOKA, 1 DAVID F. TESSLER. 2 
RUSSELL GREENBERG, 3 AND JAMES W. FOX 4 - 5 6 
ABSTRACT.—We placed light-level geolocators, on 17 Rusty Blackbirds <Euphagus carolinus) in 2009 to track their 
migrations from nest sites near Anchorage, Alaska to wintering areas and back. We recaptured three of these birds in 2010 
and found they departed breeding areas during the first hall of September, spent 72-84 days migrating to overwintenng 
areas, but only 16-30 days on their northward migration to Alaska. Birds took similar Central Flyway routes on southward 
and northward migrations, which were not previously described for this species. The birds used a series of stopover sites 
across the prairie region from southern Saskatchewan to Iowa over a 4 to 5 week period on their southward migration to 
wintering areas that spanned from South Dakota to northern Louisiana. We found upon recapture in 2010, the geolocator 
attachment harnesses had abraded the surrounding feathers on all three birds. This coupled with the low return rate (18%) 
lor instrumented birds indicates a better harness method must be developed before this technology is more widely used on 
Rusty Blackbirds. Received S February 2012. Accepted 10 June 2012. 
Understanding migratory routes and how they 
link breeding, stopover, and wintering areas is a 
key component ol effective conservation for 
declining populations of migratory birds ( Webster 
et al. 2002). 1 his task is complicated for songbirds 
by their small size, large ranges, and inconspic¬ 
uous behaviors, which make them difficult to 
effectively track using conventional mark-recap¬ 
ture techniques or radio or satellite telemetry. 
Recent advances in light-level geolocators (Bur¬ 
ger and Shaffer 2008) have provided new 
opportunities to study die migration pathways of 
songbirds (Stutchbury et al. 2009, 2011; 
Heckscher et al. 2011: Ryder et al. 2011; Bairlein 
et al. 2012; Seavy et al. 2012). We used this 
technology to track annual movements of Rusty 
Blackbirds (Euphagus carolinus), a species of 
high conservation concern (Greenberg et al. 
2011), from their breeding areas in southcentral 
Alaska to wintering areas and back. 
The Rusty Blackbird breeds in wetlands 
throughout the Nearctic boreal forest from 
northeastern North America across Canada to 
U.s. Fish and Wildlife Service. Migratory Bird 
S e ” 1 ' 1011 EilsI T ^'” r Road. Anchorage, AK 
Alaska. It winters in wooded wetlands in the 
eastern half of the United States where wide¬ 
spread wetland loss and degradation is believed lo 
be the principal cause for the 90% decline in 
population size (Greenberg and Droege 1999. 
Niven et al. 2004, Greenberg et al. 2011, Sauer 
and Link 2011). Feather isotopes suggest the 
species may comprise western and eastern popu¬ 
lations with individuals breeding from Alaska 
through central Canada wintering in the Missis¬ 
sippi Alluvial Valley, and those breeding east ot 
Manitoba wintering along the Atlantic Coastal 
Plain (Hobson et al, 2010). Little is known, 
however, about timing of migration or important 
migratory stopovers. The latter may be particu¬ 
larly important given the species is a temperate 
migrant and may spend extended periods of time 
at stopover locations before settling in wintering 
areas in the southeastern U.S. (Hamel and 
Ozdenerol 2009). 
We used geolocators to provide the first 
detailed look at the migratory movements of 
Rusty Blackbirds over an entire annual cycle. We 
also chronicle general habitats used for stopovers 
and wintering, and the potential adverse effects of 
geo locators on this species. 
J Alaska Department of Fish and Game, Wild 
Diversity Program. Anchorage, AK 99518, USA 
'Smithsonian Migratory Bird Center. Smithsonian C 
servation Biology Institule. National Zoological ? c 
Washington. D.C. 20008, USA. 
4 British Antarctic Survey, High Cross, Madingley Ro 
Cambridge CB3 0F.T, UK. 
'Migrate Technology Ltd., p. o. Box 749 Con 
Cambridge CBI 0 QY, (JK. 
6 Corresponding author; e-mail: jim_aJohnson@fws.g 
METHODS 
We captured 17 adult Rusty Blackbirds (12 
females and 5 males) in June 2009 near 
Anchorage, Alaska (61 N, 149 W) using mist 
nets placed near their nest sites. We attached 1.2-g 
light-level geolocators (model MklOS with 10- 
tiim sensor stalk at a 30 angle, British Antarctic 
Survey, Cambridge, UK) to each bird using a 
698 
