Osprey Diary 27th April: Four Eggs!

Well, if there is one thing I always say about wildlife in general and ospreys in particular- they will always surprise you now matter how much you think you know!

This female seems determined to prove all her doubters wrong and despite laying later than average this year, she has gone on to produce a bumper clutch of four eggs!

We believe this fourth egg was laid overnight again, despite our limited night nest cam view not showing any particularly strenuous behaviour by the female, so its hard to pinpoint an exact time. We were not even remotely expecting a fourth egg so didn’t zoom in close on the eggs until later this morning when we got one heck of a surprise bonus!

 This is not the first time this female has done this- she laid four eggs in 2005, and of course in the years before close up nest cams, when we had to wait until we could see the chicks heads above the nest rim, there may have been other incidents of this. However, it is considered rare in ospreys, and is a remarkable achievement.

 “Very rarely in Scotland we find four eggs laid, but this only happens when the female is in exceptionally good condition” says Osprey expert Roy Dennis, and in a survey of 495 clutches, he found only 1% had four eggs.

 A study from the 1980’s in the USA found that the amount of food a female osprey had during courtship and mating did not affect the numbers of eggs laid,  and that 30% of the study population had four eggs. (Poole 1985)

 Other studies by A.F.Poole in the USA found that fourth eggs are smaller than those laid earlier, up to10% smaller on average.

This means that a fourth egg chick will not only be more than a week younger than its older sibling, but also smaller and therefore at a considerable disadvantage. In 2005, sadly the fourth hatchling at this nest only survived a few hours.

If all chicks do hatch, there is enormous pressure on the male osprey to provide enough food for such a huge family. As far as I know there has only been one recorded incidence in Scotland of an osprey pair successfully rearing four chicks to fledging – at the Tweed valley Osprey Project in 2005.

 For us, four eggs means increased odds of any healthy surviving osprey chicks- each one precious in its own right and a very welcome addition to the UK population.

 This egg would be due to hatch in early June: 37 days = 3rd of June

 Lastly, we would love to hear from anyone who knows of any other osprey who has laid four eggs more than once- we suspect this achievement by our female may be a record first for Scotland?

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Preface

Well, if there is one thing I always say about wildlife in general and ospreys in particular- they will always surprise you now matter how much you think you know! …

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