Abstract
Delays in waterfowl autumn migration have been widely reported by hunters and ornithologists throughout North America. The implications of such delays are vast, with potential effects on the efficacy of population management, reduced social and economic opportunities, and reduced resource availability by overuse and over-grazing in key staging areas. In this study, we tested for changes in autumn migration timing for six abundant species of dabbling ducks in southern Ontario, Canada. We applied generalized linear mixed models to test for effects of year and climate indices El Nino Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO) on the Julian date of peak abundance as observed during aerial surveys conducted throughout the lower Great Lakes. Our analyses revealed delays of 11–18 days between 1968 and 2011 for four of six focal species: mallard, American black duck, American wigeon and gadwall. La Nina and El Nino events had no effect on migration timing for American black duck, American green-winged teal or American wigeon, while an increase in the annual NAO index resulted in a delayed migration for American wigeon. There was an NAO:ENSO interaction for mallard and gadwall migration; an increase in NAO advanced peak migration dates during La Nina events. However, an increase in NAO delayed migration for gadwall during the neutral phase of the ENSO and delayed migration for both species during El Nino events. Blue-winged teal and American green-winged teal showed no change in migration timing. Given that climate forecasts indicate continued positive-value phases, the autumn migrations for mallard, American black duck, gadwall and American wigeon may become increasingly delayed. Wildlife managers should use all available data, including from standardized aerial surveys, citizen science and climate models to inform and direct adaptive population management, hunting regulations, wildlife emergency response and habitat conservation.
Highlights
Climate change has yielded significant consequences for the migration phenologies of bird species across the globe (Visser and Both 2005, Knudsen et al 2011)
We examined abundance data collected via the Great Lakes Migrant Waterfowl Survey (GLMWS), an aerial survey conducted from the late 1960s to 2011, to quantify the change in autumn migration phenology for waterfowl in southern Ontario
We focused our analyses on six species of dabbling ducks that are commonly observed in large portions of Canada and the USA: mallard, American black duck, gadwall Mareca strepera, American wigeon M. americana, American greenwinged teal Anas crecca carolinensis and blue-winged teal A. discors
Summary
Climate change has yielded significant consequences for the migration phenologies of bird species across the globe (Visser and Both 2005, Knudsen et al 2011). Many migratory species depart from their wintering grounds and arrive on the breeding grounds earlier in the year compared to historically (Murphy and Noon 1991, Murphy-Klassen et al 2005, Knudsen et al 2011, Travers et al 2015) This trend has been observed among landbirds in Europe (Cotton 2003, Hüppop and Hüppop 2003, Jonzén et al 2006), Australia (Chambers et al 2014) and North America (Van Buskirk et al 2009, Francoeur 2012, Hurlbert and Liang 2012, Barton and Sandercock 2017; but see Marra et al 2005). Migration has been occurring later for some European waterfowl species since the late 1970s (Lehikoinen and Jaatinen 2012) These results may be consistent with projected changes to migration timing and distance based on climate models in North America (Notaro et al 2016). A proper understanding of the mechanisms that drive migration phenology would help identify appropriate management strategies
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