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No end to female desertion

posted Jun 24, 2011, 5:23 PM by Clemens Kuepper
In my last blog post I elaborated at length about that Snowy Plover females would stay from now on longer with the broods and stop deserting their families. Turns out that my predictions were completely wrong. Nearly all females have deserted their broods so far. The longest time a female stayed after the chicks had hatched were meagre 6 days! The males have to provide the care all by themselves. What is happening this year?

It turns out that the weather this spring was unusually cold. The water covered the area very long and breeding started late. These were bad signs because usually the chicks that hatch early in the season survive usually best and from early June on chicks have to cope with little food because the water that contains insect larvae and arthropods their main prey has evaporated. Moreover, when breeding starts late, there will be fewer nests. This year we have found only 62 until now, usually there are 30 - 70% more. Fortunately for the Snowy Plovers this year, during the period when the water evaporation was strongest,  there was an unexpected influx of brackish water which was pushed into the salt works from the North through strong winds. Although a few nests were flooded, the incoming water saved a lot of chicks from starvation. Until now we have recorded more than 25 fledglings. Until the end of the season this figure might double. Usually we get 50 fledglings only with 130 to 160 nests. This is great news for the Snowy Plovers of Bahía de Ceuta.

But you probably wonder what does this have to with deserting females? Well, female Snowy Plovers usually desert their broods when they have good perspectives for another breeding attempt. Most of these females will nest again at Ceuta or at other sites in Mexico. However, they only will desert if they feel that their mate can care for their current offspring alone. This is the case when environmental conditions are good, so that one parent can bring up the chicks alone. It means there has to be plenty of food (water), whereas predation and competition are low. Like this year in Ceuta. And the deserting females seem to get it spot on since the deserted Ceuta chicks are surviving very well!

The Least Terns at Ceuta are also doing well. We found already more than 300 nests. More than 100 have hatched already and the tern parents are busy feeding the hungry tern chicks all over the salt works. Plovers and terns breed in the same habitat but otherwise they are completely different. Tern parents feed their chicks with fish. The tern chicks will just sit in the salt works and wait for the parents to bring their meal. Because their food is full of proteins and fat tern chicks don't run around a lot, they rather invest all their energy into growing. This means they quickly become fledglings! The plover chicks on the other hand have to hunt their meals themselves. Growing takes therfore a bit longer, but their life is certainly more adventurous.