Billy Wilson sent one of those questions I get in a lot of forms, including one of my own: Do the same ducks or geese return to the same nesting spot, year after year?
Regular readers know I assume that is the case with the Canada geese pair that nests on the island of our town pond every year.
Wilson's story was this:
I live on far west side of Joliet in Kendall county. I live in a townhouse with a big retention pond about 60 yds away. I took this picture this morning (3/24/13). This is a flower pot on front porch that for the last two years provided a nest for this mallard. Now it's a third straight year. My question is, May I assume that this is the same Female year after year or maybe one of its hatchlings? I'm assuming that she saw the DU sticker on my truck and felt welcome here. Just kidding.
OK, I like that Ducks Unlimited (DU) aside.
As to the bigger question, I put it to Randy Smith, the new wetland program manager for the Illinois Department of Natural Resources.
I actually would tend to believe they are in fact the same birds. Of course that can't be proven without some sort of unique identifier (leg band, neck collar, nasal saddle, etc.). But there is some evidence from both arctic nesting goose colonies that use the same nesting location every year (birds with unique identifiers and GPS point for nest), and prairie nesting ducks that use either the same nesting structure (Delta Waterfowl Hen House - nest tube) or banded bird flushed and captured from the same nest bowl (nest site GPS coordinates) multiple years. This is most impressive to me, that a hen can not only navigate back to the same field in a constantly changing landscape of grass and agriculture and ponds drying up and expanding, but also to the exact same spot within a several hundred acre grass field.
We also know that ducks are very philopatric, that is they return to the same places to breed where they were successful previously, and juveniles often return to the same places to breed as where they fledged.
I think it's very likely that in the instances you mention, it could be the same bird nesting in those spots year after year.
Very interesting and I learned more than a few things, including looking up philopatric.
(of an animal or species) tending to return to or remain near a particular site or area.
This question was actually used in the mail bag. But I thought the answer worth expanding out online as a Wild of the Week.