Our I.iviuf; Rcsinirces — Glulnil Climate Chemise 



.i9l 



May 30 



J Apr 30 



ra Mar 31 



Mar 01 



Fig. 3. Trend for purple martin {Progne siihis) from the 

 Cayuga Lake basin of central New York showing a clear 

 tendency for earlier spnng arrival. The negative slope ot 

 the trend is significant at f < 0.005. 



May 30 



o ° o „o o 



^^^^^^^5^^ 



O GO 



Apr 30 - 



Sn^gi.3.| Blackpoll warbler y=159-0.13x 



S /?2 = 64% 



Mar 01 



03 



~i I ' r 



39 57 



Year 



75 



93 



Fig. 4. Trend for hlackpoll warhler (Dendrnica striata) 

 from the Cayuga Lake basin of central New York, showing 

 no tendency for earlier spring arrival. The slope of the 

 trend is not significantly difterent from zero. 



Migratory Landbirds 



Records of first sightings of spring migrants 

 from the Cayuga Lake basin of central New 

 York are from 1903 to the present and represent 

 130 species. More than 5,000 first airival dates 

 were examined for 76 species of migratory 

 landbirds. excluding waterfowl, hawks, and 

 shorebirds. Thirty-nine species (51%) showed 

 90-year trends of significantly earlier {P < 0.05) 

 arrival, with an average shift of about 5.5 

 days/50 yr (for example, see Fig. 3). Thirty-five 

 species (46%) showed no significant change (P 

 < 0.05) in dates of first spring arrival (Fig. 4). 

 Louisiana waterthrush and mourning warbler 

 {Oporomis phihiJelphia) were the only species 

 showing significant trends (P < 0.05) toward 

 later spring arrival dates. 



Of those species showing significantly earli- 

 er arrival dates, 85% are long-distance 

 Neotropical migrants, which normally overwin- 

 ter in Central and South America. For the 

 Mohonk Preserve data, 6 of 10 migratory bird 

 species examined showed significant trends 

 toward earlier arrival. For the western 



Allegheny Plateau, First-anival data, covering a 

 40-year period beginning in 1952, were avail- 

 able for two species of birds, Louisiana 

 watetlhrush and solitary vireo. Both species 

 tended to earlier arrival. 



Conclusions 



The trends reported here toward earlier 

 arrival dates for migratory birds and earlier 

 blooming dates for spring wildfiowers are con- 

 cun'ent with patterns of climatic warming and 

 consistent with what might be expected in the 

 context of global warming. At the same time, 

 local changes in land cover, with the forested 

 area of the region increasing by more than 30% 

 since 1900, may provide greater amounts of 

 suitable habitat for attracting and holding 

 migrating landbirds, thereby contributing to 

 observed patterns of change in migratory 

 behavior. 



It is noteworthy that only two bird species 

 examined, and no plant species, showed trends 

 to either later spring anival or later blooming. If 

 explanations of trends for only one of these two 

 major groups were sought, alternative explana- 

 tions could be advanced, such as expansion of 

 bird ranges due to changes in land use (see Root 

 and Weckstein, this section). In addition, a 

 recent examination of dates of fall departure for 

 migrating birds in Germany (Gatter 1992) 

 shows later fall departures. Such fall trends 

 would be expected in the context of climatic 

 warming and agree with the spring trends we 

 report. 



Given the patterns reported here, climate 

 change is the one variable affecting diverse 

 groups of organisms that offers a rational and 

 parsimonious explanation for the observed 

 changes in timing of migration in birds and 

 blooming in plants we and others have 

 observed. Research either planned or in 

 progress includes analyzing additional data sets 

 as well as more sophisticated statistical analy- 

 sis; determining the species most appropriate 

 for monitoring climate change; finding and ana- 

 lyzing data sets that describe the phenology of 

 other taxa; and possibly extending the study to 

 other locations. 



References 



Gates, D.M. 1993. Climate change and its biological conse- 

 quences. Sinauer Associates, New York. 280 pp. 



Gatter. W. 1992. Zugzeiten und zugmuster ini herbst: ein- 

 tluss des treibhauseffekts auf den vogelzug. Journal fiir 

 Omithologie 133:427-436. 



Schwartz. M.D. 1990. Detectmg the onset of spring: a pos- 

 sible application of phenological models. Climate Res. 

 1:23-29. 



Wiegand. K.M., and A.J. Eames. 1925. The flora of the 

 Cayuga Lake basin. New York. Cornell University 

 Agricultural Experiment Station Memoir 92. 491 pp. 



For further information: 



Ray T. Oglesby 



Cornell University 



Department of Natural Resources 



New York Cooperative Fish and 



Wildlife Research Unit 



Ithaca. NY 14853 



