What Goes on in a Duck’s Hypothalamus?

How do they know? Each year, within 48 hours of the winter solstice the ducks start laying. Not all of them and not a huge number of eggs, but as sure as you can say ‘here comes the sun’ those girls have a meeting, set up a schedule, and fire up the production line.

This year, the solstice was on December 21st and the first duck egg appeared on the 23rd. We are now up to about four a day from my flock of 25 even though it has been cloudy, dull, and rainy. How do the ducks know that we are gaining a few precious minutes from day to day? I can barely tell when the day begins or ends when it’s this gloomy! What I do know is they will produce duck eggs from now until some mysterious meeting in late July when they take off their hair nets and shut down the line until the next winter solstice rolls around.

When they hit their stride and the new girls (from last year’s hatch) get broken in, I should get between two and three dozen a day during their peak laying months of March, April and May. There are always a couple of super stealthy ducks who manage, somehow, to shoehorn themselves into impossibly tiny spaces to sneakily lay a clutch of eggs. When a couple of them gang up on me and share a secret spot, this can result in a huge clutch of accidental ducklings. The females are welcome to stay, but the drakes get large and argumentative and exhaust the poor females and unless we are eating them ourselves I have to haul the extra boys three hours north to the closest processor that will handle ducks [this unfortunate situation is the subject for another post on another day].

I’ve long been impressed with the ducks’ ability to detect the changing length of the day but didn’t really know what the mechanism was. Turns out it has to do with light receptors located deep in the brain in the hypothalamus. Bird skulls are pretty thin and enough light passes through the bone to reach these receptors, which then stimulate hormone production relating to egg production and mating behaviour.

For more details, this University of Oxford article is interesting.

This could also explain why ambient light from cities is messing up wild bird breeding schedules. Too much overnight light in urban areas also causes more nocturnal activity and changes in breeding patterns in city birds. City birds also have altered levels of melatonin, a change related to altered light levels. For a bit more information about the melatonin findings, here’s an article on the Science Daily website.

If I were trying to maximize my production I would add light to the ducks’ environment to trick them into starting earlier in the season and laying longer. I haven’t studied this scientifically, but it makes sense to me that the ducks might have longer productive lives over the long haul if I let them take a break each year the way nature has worked things out. I may not get every last possible egg from my girls each year, but they seem to keep going year after year and some of the older ducks are fantastic mothers.

[And, finally, a quick follow-up note to yesterday’s post… Not only did the poll come in with a resounding ‘keep doing what you’re doing’ result, some of my favourite bloggers left lovely comments… In case you aren’t following the comments thread, I’ve cut and pasted my response to the responses below… Thank you to everyone who took the time to share your thoughts/votes!

Oh my wonderful bloggy friends – thank you!! I read all your comments and as I did so could not help but smile and nod and marvel at just how cool this community is. Yes, of course Wendell Berry is who he is because he has dirt under his fingernails AND writes poetry – and yes, I would love to know ALL about the secret lives of farmers 400 years ago (or, today – in Botswana, for that matter), and yes, I agree that a blog that is all about one narrow subject and only that one subject tends to get a bit tedious… It is fascinating to me that all these caring, thoughtful comments are, without exception, from bloggers whose blogs I read and enjoy precisely because of their variety and personality… We are not uni-dimensional, so why should our blogs be so? It all seems so very obvious when you point it out like that! I feel hugely relieved and will carry on and not fret again… for a while… until I fret again. At which point, you will all promptly set me straight. ]