More Osprey Q and A: 27th April

Q:  At night, the structure that holds the nest creaks terribly in the wind- the creaking noise wakes her and at times it appears to cause her concern …I am worried the structure will fall down altogether! I am wondering whether it is possible to add extra soil or something around the base of the pole, pylon, tree, or whatever is supporting her nest? At present, it sways in the wind, and I fear it will collapse!

A: Please don’t be concerned about the osprey in her tree top eyrie- she is perfectly safe. The nest is on a huge strong Scots Pine tree which is probably a hundred years old, which has withstood many terrible storms unscathed. The way the tree bends with the wind actually makes it more safe- it flexes naturally rather than breaks. The osprey nest has some metal reinforcing rods underneath and is securely attached to the branches and trunk and cannot fall- we check this every winter when the birds are away, as it illegal and unethical to approach the nest when the birds are in residence. We have watched this female weather some really bad storms on the nest over the last 24 years and she has never given up or been dislodged from it yet- she is one strong determined bird!

She frequently wakes during the night and is vigilant to all sorts of sounds such as deer moving beneath the tree, other nocturnal birds, and pine martens etc. She is aware but not distressed by these- she does not show any typical fear, stress or alarm behaviours so we don’t believe she is worried.

Q: How much on average, does an osprey nest weigh?

A: Good question- I don’t have an accurate answer I’m afraid. Osprey nests here in the UK range from about 4 -6 feet in diameter.  How deep they are depends on how long they have been in situ- the largest I have seen was nearly 5 foot in depth. As it is made up of tightly woven sticks, lined with turf, moss and other soft materials that can absorb considerable water, I should think it could all add up to a large weight. What I can tell you is that when school children and I attempt to make a life-size model of an osprey nest, it takes a huge amount of sticks and is a lot of work!

Q: How are the birds coping with the really wet weather? I noticed the female was soaked through last night and had to get up and shake herself out!

A: Our ospreys have coped with almost every sort of weather over the years on this nest from storms, to hail and snow, to mini heat waves- they are remarkably resilient birds. They are not truly waterproof however, and their feathers can get soaked which is why they shake after diving or after prolonged rain. You will also notice them fluffing themselves up when its very cold in order to trap more warm air close to their skin, and panting to expel excess heat if necessary- or taking a dip to cool down!

Q; I am wondering if ‘Lady’ is developing dementia in her old age with her unusual behaviour or maybe she knows that her eggs are infertile perhaps?

A: There is no doubt our female’s behaviour is a bit unusual- spending so long off the nest and likely fishing for herself, but not at all unheard of in ospreys. We are not unduly worried and have every faith in her parenting abilities. In the past she has incubated eggs normally all season that turned out to be infertile so we don’t believe she can tell at this stage. There are no studies of old age behaviour in raptors like ospreys I’m afraid- this is the first time we’ve been able to study a old bird in such detail.

Q: It has occurred to me that maybe ‘Lady’ only returns as far as Spain each year hence her longevity  – not having to encounter the Sahara and the high range of  mountains further south. What are the teams thoughts on this?

 A: We have discussed this theory many times and it is perfectly plausible- especially as we now know from colleagues in southern France and Spain that ospreys began overwintering there from the early 1990’s. However, we have no way of knowing for sure as our female is not tagged or tracked. This is one reason we have begun satellite tracking her offspring which should give us clues as the theory is youngsters inherit their wintering destination from their parents.

Ranger Emma

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Q:  At night, the structure that holds the nest creaks terribly in the wind- the creaking noise wakes her and at times it appears to cause her concern …I am …

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