The Wilson Journal of Ornithology 123(3): 5 57-566, 2011 
LONG-TERM SHIFTS IN AUTUMN MIGRATION BY SONGBIRDS AT A 
COASTAL EASTERN NORTH AMERICAN STOPOVER SITE 
SUSAN B. SMITH' 2,3 AND PETER W. C. PATON' 
ABSTRACT.—We investigated long-term trends in mean autumn capture dales ot 19 s P e ‘ri® s °|anV^OoTat a 
.1 long-distance migrants and eight short-distance migrants. Birds were cap 
banding station in southern Rhode Island. We detected annual trends ini t ■e « g ^ | onp -distance migrants and 50% of 
4 seven species significantly delayed by an average ut 3.0 days per i • - long-term shifts in autumn 
ihon-distance migrants studied significantly delayed migration. e 0un ’ ® V ' _ t nearannua l trends. Mean autumn 
migration timing for seven species and mean capture dates ot five species ex i i annual capture rates for some 
lanperature was an important factor in explaining annual trends for eight species. > g ' . ■ autumn migration 
'teoes may have an £ual or greater role than year or temperature in explaining 
Lg.0u analysis SggestsOta. some migratory bird species are now departing the reg^n later 
Important differences among species and regions are likely to influence spec.es-specfic responses to changes 
patterns. Received 30 August 2010. Accepted 9 February 2 Oil. 
The rise in global temperatures in recent 
decades has affected the phenology of many 
biological events across a variety of organisms 
and trophic levels (Walther et al. 2002, Parmesan 
and Yohe 2003, Visser and Both 2005). Avian 
migration may be particularly sensitive to climate 
change because many species rely on environ¬ 
mental stimuli, in addition to intrinsic cues, to 
initiate major events during their annual cycle. 
There is growing evidence that many European 
passerines are responding to annual fluctuations in 
local air temperatures and large-scale climatic 
perturbations by shifting the timing of annual 
migrations (Lehikoinen el al. 2004, Gienapp et al. 
2007, Gordo 2007, Rubolini et al. 2007). Passer¬ 
ines in North America, where the rate ot climate 
change is not as pronounced as in Europe, exhibit 
a trend towards earlier spring migration, although 
not as consistently as in most European studies 
lGordo 2007, MacMynowski et al. 2007. Miller- 
Rushing et al. 2008, Van Buskirk el al. 2009). The 
ability of birds to adapt to climate change by 
adjusting timing of spring migration has clear 
consequences for breeding success because mis¬ 
timing of breeding events with peak food 
resources has been linked to population declines 
<Both et al. 2006, Visser et al. 2006, Leech and 
Crick 2007, Mpller et al. 2008). 
The potential effects of global warming trends 
Department of Natural Resources Science, Kingston, RI 
02881, USA. 
Current address: School of Biological and Medical 
Sciences, Rochester Institute of Technology, Rochester, NY 
14623, USA. 
3 Corresponding author; e-mail: sbssbi@rit.edu 
on timing of autumn migration are inherently 
more complex and fewer studies have examined 
changes in autumn departure or migration passage 
dates'. European and North America studies of the 
chronology of passerine migration in autumn have 
provided mixed results. Some studies reported 
delays or advances while others have reported an 
absence of long-term trends (Lehikoinen et al. 
2004, Mills 2005, Gordo 2007, MacMynowski 
and Root 2007, Van Buskirk et al. 2009). In 
addition, the strength and direction of long-term 
trends and phenological responses to climate 
change appear to be variable among species 
(Jenni and Kery 2003. T 0 ttrup et al. 2006, Thorup 
et al. 2007). . L 
We analyzed annual variation m the mean 
autumn passage dates of 19 passerine species 
during stopover in southern Rhode ^and us ng 
45 years of data from the Kingston Wildlife 
Research Station, one of the longest operational 
migration monitoring stations m eastern North 
America. Our objectives were to: (U examine 
whether mean passage dates of migrating passer¬ 
ines are changing over time. ( 2 ) assess If variation 
in migration chronology could be explained by 
annual changes in local autumn temperatures, and 
( 3 ) consider the influence ot annual capture rates 
on our interpretations because fluctuations in 
population sizes may influence estimates ot 
annual migration timing (Miller-Rushing et al. 
2008). 
METHODS 
Study Site .—We conducted field work at the 
Kingston Wildlife Research Station (KWRS) in 
South Kingstown, Rhode Island, USA (41 27 N, 
557 
