Osprey Diary Sat April 13th

 The last couple of days on our Loch of the Lowes osprey nest have been alternatively routine, and exciting- and as we all know, these birds always keep us guessing and learning every year.

Our female continues to base herself at the nest (though she spent a lot of time today elsewhere, especially after chasing off an osprey intruder this morning) and to do the usual nest renovations. The male continues to bring in more sticks and moss, as well as fish for his mate- though he still sometimes touches down with them teasingly and takes off again without sharing.

Some people have noticed our female doing a  lot of preening lately- this is probably because she is preparing to moult ( as is normal for females on the nest)  and new feathers must be starting to push through from underneath.

 Both birds have been doing something a little more unusual, in spending some time each day on another tree nearby- the one affectionately known here as “Flat Top”. This Scots pine tree lost its crown in last winter’s storms and now has some dead branches at the top, with a great view both of the main nest, and both lochs. It’s no wonder the birds have been using it as a vantage point and an eating perch. However, they have also mated on this tree and the male particularly seems to like it- let’s hope he’s not getting any funny ideas about moving the nest!

 Here’s some more osprey egg questions:

 Q: When can we expect eggs?

A: Our resident female osprey has laid eggs in the past as early as the 1st of April and as late as the beginning of May, depending on her arrival and mating dates.  She laid her first egg last year around this time after arrive exactly the same date.  Estimates of the interval between first mating and first egg laying in ospreys are quoted as widely as 7- 16 days so we are still within the normal window.

 Q: Could she be too old to lay eggs or might they be infertile?  

A: We don’t know- we have never been able to study an osprey of this veteran age in such detail. As she is still interested in mating, we believe she is still capable, though her fertility may not be as good as a younger bird- only time will tell.

 Q:  How many eggs do Ospreys lay?

A: Two or three is the usual number of eggs for an established breeding pair of Ospreys.  Rarely four eggs are laid, although either these may not all hatch, nor all survive to fledging. The eggs are laid individually one to three days apart, though they have been up to 6 days.

 Q: How big are the eggs?

A: Surprisingly, osprey eggs are only the size of a large hens or duck egg. 

Each of the eggs is unique and is a combination of off-white to pinkish or buff background, with mottled dark brown or reddish splotches. Some eggs have a uniform mottled appearance while some can have more of this reddish brown colouration at one end.

 Q: How long do they incubate for?

A: The general rule is 5 to 6 weeks (35-42 days), the average being 37 to 39 days.

 Q:  Can an Osprey lay eggs that haven’t been fertilized by a male?

A: I don’t believe so, in that female ospreys do not lay eggs on nests without males (unlike chickens) needing the stimulus of copulation to trigger egg production. However, if there is something wrong with either the egg, or the sperm, it is possible for an egg to be a ‘dud’.

 Q: What will happen if she doesn’t lay any eggs?

A: We don’t know – as this has never before happened with this female. She may lose interest in the nest or perhaps wander off, and the male may then lose interest in her and either begin building a frustration eerie, or leave too. Let’s hope it doesn’t come to this though.

Lastly a shout out to Kevin Hacker, on of our volunteers and the guest host of our Photography course here this weekend- Happy Birthday Kev! Don’t worry if you missed out, Kevin will be doing another great course in June for wildlife photography enthusiasts.

Help protect Scotland’s wildlife

Our work to save Scotland’s wildlife is made possible thanks to the generosity of our members and supporters.

Join today from just £3 a month to help protect the species you love.

Join today


 The last couple of days on our Loch of the Lowes osprey nest have been alternatively routine, and exciting- and as we all know, these birds always keep us guessing …

Posted in

Blogs -

Stay up to date with the Scottish Wildlife Trust by subscribing to our mailing list Subscribe now

Back to top