Black-headed ducks
These ducks may be brown, dull, and mousey in many aspects, but they are absolutely stunning in others!
The black-headed duck or "cuckoo duck" is to me the most fascinating and innovative of all the birds we keep at Slimbridge. The birds live solitary lives, spending much of the year alone and only coming together to mate. The male has a simple throat gurgle and inflation, which although not very striking in the scheme of things appears to do the job! Black-headed duck are pretty verile and copulation is generally very successful. Sperm is hoarded by the female and she will lay three or four eggs in the nests of any species within reach; from different species of waterfowl to moorhens and coots! Neither bird then takes any further part in parenting and disappear off from whence they came.
The eggs sit under the host bird and are turned and incubated along with the host eggs. Upon hatching the little guys snooze for 12 hours or so absorbing the yolk sack and drying off, before jumping ship as it were and just heading off into the wilderness to rear themselves!
In the 90's staff were collecting around 12-14 eggs a year from host nesting species including Rosybill and Puna from our South American pampas pen. They were such an assumed acquisition that soon they were endlessly giving pairs away! Collected up fresh and put under bantams the eggs proved amazingly resilient to addle and we soon discovered they could be put under just about anything and still hatch very successfully. Over time however we soon became so used to passing them on that we were not adequately aware of the dangers that were afoot. the host birds in the pampas pen were aging and nesting females became fewer. Suddenly there was nowhere for them to lay their eggs and after two difficult years everything just stopped laying altogether.
Our experience of incubating and rearing from fresh is that the incubation period is in fact 19-22 days. The eggs are easy to identify for although being classically bulbous and white the shell has a visible porosity to it and are often punctuated by blocked dirty pores. The hatch is pretty quick, and the duckling is distinctive in that it makes no coop mates or friends, and is an individual from the first. It was found that wet-rearing was ideal with species such as white-headed duck and Maccoa, and that they were typically silent. We cannot prove that calling does not occur within the egg and after, but considering that in the wild they need not coordinate their hatch with any other under the host and they swim off alone to rear themselves in the wilderness, we had assumed they had no need of one. Mark Hulme once did a study for WWT on alarm calls, and although the BHD duckling was often seen following the host briefly during periods of stress, not a single note was uttered.
This was highlighted to us just 2 weeks ago, as when the duckling that had hatched unexpectedly under a call duck was being rounded up, when it went to ground it was totally and utterly as silent as the grave. As our breeding aviaries are not as fruitful as their natural homeland, self-rearing was never an option! Here he is safe and sound in the company of some little stifftails.
17/06/11 Kathy Valier: Pretty amazing that the hatchlings make it on their own. That must be the ultimate in precociousness
