Hi all, Iris is showing some interesting changes in behavior the last few days. You may have noticed that she is starting to spend more time off the nest away from her chicks. This is probably because the chicks are so large now and dont need her as much to shelter them. But also, Iris is probably pretty worn out now. Even though it might seem like Stanley has a much more active and demanding job fishing, being a mother Osprey seems to be more stressful. Lately when it has been very hot and sunny, Iris spends virtually all day as mombrella - standing in the full sun with her wings drooped to provide shade for her chicks. This has to be hard, and over the course of the breeding season female Ospreys loose much more mass than males. Here is a graph of the body masses of female (upper line) and male (lower line) Ospreys over the course of the breeding season. This is from great work of Alan Poole - one of the leading Osprey experts. He set up perches on Osprey nests with electronic balances, so every time the birds perched they weighed themselves. You can see that females tend to loose about 200 grams during the breeding season - this is about 10% of their mass! In contrast, males loose about 80 grams, or about 5% of their body mass. So by the end of the breeding season the female Ospreys are probably pretty worn out. Iris will probably migrate first, and leave Stanley to take care of the chicks on his own for a few weeks. She probably wont leave for another 3-4 weeks, but her behavior is changing these last few days. Cheers, Erick Greene
Posted on: Thu, 31 Jul 2014 15:57:54 +0000
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