Ecology of wintering Canada geese in the greater Chicago metropolitan area
Canada geese (Branta canadensis) breed in subarctic and temperate areas of North America, but both populations typically winter in temperate regions of the northern United States. During winter, Canada geese are increasingly using urban areas, but data are lacking on habitat use and selection, movements, potential thermal benefits of selected habitats, and survival of Canada geese during late autumn and winter in urban areas. I captured Canada geese during November‒February 2014‒2016 in the Greater Chicago Metropolitan Area (GCMA) in northeastern, Illinois, USA and fitted 41 geese with solar-powered GPS transmitters. Neck collar-mounted transmitters operated on the cellular phone network and collected hourly locations (n = 39,392). Canada geese selected green spaces (59.8%) in greater proportion than available (14%), but I also documented geese using novel habitats such as rooftops and rail yards (i.e., industrial urban; 11.3%). Habitat use shifted away from green spaces (36%) to industrial urban habitats (10.4%), riverine (12.8%), and deep-water habitats (37.8%) as temperatures decreased below the lower critical limit for Canada geese (i.e., temperature at which increased thermoregulatory costs are incurred to maintain core body temperature). During periods when temperature decreased and snow depth increased geese increasingly used industrial urban habitats. Both snow depth and minimum daily temperatures were associated with decreased movement distances within habitats. Movements by Canada geese within rail yard (x̅ = 224.0 m, SE = 13.0) and green space habitats (x̅ = 145.6 m, SE = 3.4) were the longest for any habitat type, while movements by geese in deep-water habitats (x̅ = 85.7 m, SE = 3) and rooftop habitats (x̅ = 52.9 m, SE = 5.5) were the shortest. When temperatures were below the lower critical temperature (-6 ⁰C) Canada geese transitioned from deep-water to green space habitat in greater proportion than all other possible transitions between habitat types. Proportion of use of green space habitat increased during diurnal hours. Both deep-water and riverine habitats had greater proportional use during earlier morning hours than later in the day. Conversely, proportional use increased from midday to early evening in industrial urban habitat where proportional use increased during midday to early evening. All habitats had similar daily low temperatures, deep-water (+3.5 ⁰C) and industrial urban habitat (+3.2 ⁰C) did have warmer daily high temperatures than green space. The majority of transmittered Canada geese (85%) wintering in the GCMA never migrated south and no geese made foraging flights outside of the GCMA to agricultural fields. Winter survival was 100% for Canada geese remaining in the GCMA and 48% for geese that left the GCMA, with all mortality due to hunting. Since geese did not make foraging flights to agricultural fields, hunting may not be a viable option to reduce urban populations or change movement patterns during winter. Future research should test targeted harassment at industrial urban habitats, such as rooftops and deep-water habitats to see if Canada geese could be forced to leave urban areas.
Canada geese, urban, habitat selection, survival, movements
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign