creching in waterfowl

I know some waterfowl such as eiders form creches where ducklings from several broods join up and are looked after by one or more of the female parents at a time.

Here's what looks like a Mallard female with, count them, 19 ducklings in tow (did I get the count right?)! Is 19 just too many ducklings to be from one brood? Do dabblers like Mallards creche?

Image was made at the Sackville Waterfowl Park on 11 July 2008.

PS of course the age-old evolutionary question with apparently altruistic behaviours like creching is what does the aid-giver get out of it?

John,

We see a similar situation with Canada Geese here in the Pacific Northwest. Sometimes groups of young geese upwards of 50 will gather with only 2 - 6 adults in attendance. The other adult geese will fly north and molt and return prior to the fall migration.

Jim

I wondered this same thing earlier in the spring when I saw two Canada geese with 19 babies in tow. I couldn't believe they all came from the same creche as some looked just a bit older in development - yet, there they were, all following the one set of parents.

Interesting image John. From what I've seen Mallard nests usually result in 5-9 ducklings...but I have heard of egg dumping where other females will add nests to another nest. I'm not sure if that is a possible explanation in this case or not. Could a single female actually incubate 19 eggs?

Interesting question, which leads to another question. Do we anthropomorphize if we assume they have to get something out of caring for other bird's chicks?

Hi John

While Eiders genuinely creche their ducklings, other species have a darker side with dominent females actually 'kid (duckling) napping' other broods.

Goosander (Common Merganser) are particularly prone to this activity & sometimes acquire ducklings of other species, e.g. Goldeneye. It is believed that these mothers considerably improve their own ducklings survival chances by artificially increasing the brood size.

Cheers: Wayne

Very interesting Wayne. I had never heard this. I suppose so long as the kidnapped duckling survival stays the same there is no great cost to the parents who lose their kids.