Wildlife Diary Tues 26th June

 Our Osprey chick is five weeks old and developing well- not only is it a very healthy size, it is passing each developmental milestone with flying colours! After a few days off, I hardly recognized the wee one as it is much more like a proper osprey now, with feathers coming in everywhere. Whilst the tips of the feathers are visible and fluffy, underneath each is still growing through the waxy sheath, and so it is still not very waterproof or thermally insulating, hence the female still keeping it well covered in the rain, and at night.

 We have been asked why the chick is a speckled appearance, and the answer is camouflage: if you have ever seen an osprey parent give a real alarm call to the chicks, it prompts them to lay completely flat and still in the nest as a defense: and they effectively disappear into the mottled nest, at least to an aerial predators eyes.

 Please remember if you have an osprey question, please consult our FAQ tab at the top of this page. We are hoping to update this with new questions very soon- meanwhile take a moment to scroll back through the blog to see what has already been answered recently. If you still can’t find the answer, feel free to email us on ospreys@swt.org.uk

 Here are some more recent Osprey Q and A’s:

 Q: When will the chick fly?

A: By about seven weeks of age, osprey chicks are ready to test their wings for the first time. They often exercise on the edge of the nest and lift off in short hops before taking off properly for the first time. To encourage the chicks to fledge, the adults will bring less and less fish back to the nest– effectively starving them off the nest.

Q: What age are Osprey chicks ringed and satellite tagged?

A: The chicks are often ringed at around 6 weeks of age.  By this time their leg bones are fully formed, and the parents have had time to bond with them so that they won’t be abandoned as a result of the disturbance, but they are still too young to flap accidentally out of the nest. This should be the only time they are ever handled or disturbed by humans at the nest site. Information on size, weight, sex, health, DNA  etc is often collected during this brief process.   This is also when Satellite tracking devices can be attached to the birds.

Q: What Gender is the chick and does the darker breast on it mean it’s female?

A: The short answer is that we don’t know yet if it is male or female. There is no ‘external plumbing’ in birds, and in Ospreys no clear difference in plumage (unlike say in ducks) so clues are very small. Generally female Ospreys will end up 30% larger than the males but in chicks with different ages and feeding, this can be misleading as an older well fed male may be larger than a poorly nourished or younger female. Experts can usually tell at ringing if the chick has thicker legs that it is a female- but the only way to be 100% sure is a DNA test, or waiting for 3 years to see its behaviour at mating!  Whilst in adults, the females generally have darker breasts than males, this is not always reliable. In chicks, plumage can change a huge amount in the first two years so it is not a reliable indicator of gender.

Q: Why is the chick lying on the eggs- is it trying to mimic its parents incubating behaviour?

A: The chick is using the eggs as a handy support- almost like a pillow! It is treating them as just part of the furniture in the nest and something convenient to lean on, not really incubating them. Having said that, all young animals and birds learn partly from mimicry, which is why the chick has been moving sticks on its own in the nest.  

Q: Why haven’t the birds gotten rid of the unhatched eggs from the nest?

A: We don’t really know- all we can say is that can’t be too smelly or a health risk, otherwise our fastidiously clean female would have removed them by now. Sometimes unhatched eggs remain in the nest for many weeks, and if they survive unbroken until after the chick fledges, we will remove them under special scientific license to analyze what went wrong with them.

Lastly a fun picture by a visitor Lesley Garven, of how our brids keep the nest so clean:

Our male Osprey by Lesley Garven

Preface

 Our Osprey chick is five weeks old and developing well- not only is it a very healthy size, it is passing each developmental milestone with flying colours! After a few …

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