Oh baby baby

It’s that time of year.  While all the songbirds are flying around singing and making a general spectacle of themselves, the ducks have apparently been quietly going at it for awhile.  Running through Freedom Park yesterday, I came across a pair of Mallards escorting their babies (13 in all) up Little Sugar Creek.  The chicks were all following mom, while the male brought up the rear.

Two things really struck me as I watched those kids work hard to keep up with mom (and they really did have to work!  When she took them across the center of the stream, the current spread their little clump out into a long line.  It wasn’t until they could get back to the edge that the chicks in the back caught up to the group).  First of all, thirteen kids seems to me a pretty hefty number.  Mallards aren’t known for being brood parasites, so I’m going to assume that all of those chicks belong to the female that was leading them.  It seems that clutch size in female Mallards is more of a function of time of year than anything else.  They have an ability to lay a large number of eggs, but clutches that are laid earlier in the season tend to be larger.

Krapu, G.L. 1981.  The role of nutrient reserves in Mallard reproduction.  Auk 98:  29-38.

Krapu found that females lose a fair bit of body weight as they lay their eggs and that clutches laid early in the season were larger than those laid later in the season.  Granted, he did study them in North Dakota, where the birds are likely under more stress, but it’s a good pattern to follow.  Other people who’ve worked on Mallards found that food quality doesn’t really affect how many eggs the birds laid.  In a lab experiment, Eldridge and Krapu found that diet doesn’t affect the number of eggs that are laid.  It only affects the size of the eggs (and the protein concentration of the eggs).

Eldridge, J.L. and G.L. Krapu.  1988 The influence of diet quality on clutch size and laying pattern in Mallards.  Auk 105:  102-110.

Now the other interesting observation was that while there was one female with the kids and one male following along behind, there were four single males sitting nearby on the bank.  That’s quite an unfortunate sex ratio for those birds and brings to mind a question.  Was the male at the back of the train really the father of the chicks?  That’s a hard thing for me to answer without doing some DNA analysis (and since I was on a run, I wasn’t carrying that sort of equipment).  What I can say, though, is that some people working in Canada found that 25% of Mallard nests had chicks that came from multiple fathers.

Evarts, S. and C.J. Williams.  1987.  Multiple paternity in a wild population of Mallards.  Auk 104: 597-602.  

Mallards are an interesting species in that sense, in that a lot of descriptions of forced copulation began from studying this species.  But without getting into that topic at this point, it still opens the door for that male in the back of the train to be taking care of a lot of kids who aren’t his own.  They’d just better hope that duck university is cheap.


About thomasbiology

I'm an Associate Professor of Biology at Queens University of Charlotte with a background in animal behavior with an emphasis in bird song. I've got two secret goals with this blog (well, since I'm sharing them, they're not so secret): 1. To encourage people to look at the natural world around them- not just as a hiking destination, but to notice all the little things moving around them all the time; and 2. To show some of the science that relates to these little things moving around. There's some really fascinating research out there that so few people get to see.
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