Identity crisis: greater snow geese altering migratory pathways and following their 'lesser cousins'

Identity crisis: greater snow geese altering migratory pathways and following their ‘lesser cousins’

A Hybrid is the result of two species successfully having offspring; one example is the liger, a cross between a tiger and a lion.

http://wildlifewaystation.org/animals/individual/namibia-the-ligress

There are numbers of animals that are a product of two species becoming one; and often an illegitimate one, unable to reproduce. Hybrids in nature are not entirely uncommon, particularly within waterfowl communities.

Here is a Snow Goose, and what is likely a Cackling Goose (subspecies of Canada goose) Someone even blogs about it; http://huntfowl.com/blog/12-rare-waterfowl-hybrids-every-hunter-wishes-theyve-bagged/4/

For subspecies of the Canada Goose see

Arctic Facts: How many kinds of geese are there in the Arctic?

What stressors occur in the environment or individual physiology that would encourage hybridization? How important is this kind of genetic mixing? Is is good, bad, both? I started thinking about these questions when a band recovery came across my desk by email. I covered the hunter’s name to protect his identity but this report indicates a Greater Snow Goose (Chen caerulescens atlantica) was harvested in Arkansas during the Spring Conservation Hunt this past February 2017.

Compare the location of the recovery to the most commonly sourced location for wintering and breeding areas of Greater Snow Geese.

Modified from the map obtained through Canadian Wildlife Federation

So what was this bird doing over there? After consulting with goose biologists much more experienced than myself, I realized that this isn’t the first time a Greater Snow Goose has been harvested so far from their ‘proper’ wintering area. Band recoveries indicate that many individuals have followed their Lesser Snow Goose ‘cousins’ (Chen caerulescens caerulescens) further south west. If you look at the outlier band recoveries for the Greater Snow Goose (map below on left) and compare those to the Lesser (on the right) it would seem those individual Greaters are overlapping in Lesser Snow Goose wintering areas.

 

As Snow Goose numbers increase in North America, a conservation and agriculture nightmare (in some opinions) breeding colonies are merging, expanding and in general becoming closer in proximity to one another on the Arctic tundra. Massive flocks of birds merge in areas heading south. Specifically, there is now a good overlap of contact in the northern part of Foxe Basin and on the northwest end of Baffin Island between the Mid-continent Lesser Snow Geese and Greater Snow Goose population. There is mixing, in particular, of young and failed breeding birds during early migration. “It is likely that this bird and others like it form an association with a bird or birds (flock) from the predominantly Lesser Snow Goose stocks and then follow them to the mid-continent wintering areas.“-Snow Goose Biologist. It is also unknown if there is direct mixing between individuals with Lessers and Greaters producing young.

Overlapping or even direct mixing of these species could mean several things; including extensions of the wintering areas between the two species, hybridization, and with that alterations in behaviour. We don’t currently know the long term consequences of these geese mixing but it definitely highlights the importance of banding operations and long term research studies, particularly in the Arctic.

 

 

 

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