Osprey Chat Thread for May 2015

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  • The question of when is the last date for laying osprey eggs?

    Well I have decided to work it out the other way around. viz. How old does an osprey chick have to be to migrate?  Well I would say around 80 days old.

    If you add 37 days for incubation that makes 117 days. 

    Assuming at 30th September is the very last time that a young osprey could migrate. 

    Now there 30 days in September, 31 days in August, 31 days in July and 30 days in June  a total of  120 days. 

    So it would seem that 31 May is the very latest that an egg could be laid and there be any realistic prospect of the chick having a successful migration.

  • That's an interesting analysis TIGER.  I don't think I've seen such a late date suggested before, but it makes complete sense!

    Do you know of any eggs laid around the end of May and chicks which successfully fledged?

    Birdie's DU Summaries 2018   https://www.imagicat.com/

  • SheilaFE said:

    That's an interesting analysis TIGER.  I don't think I've seen such a late date suggested before, but it makes complete sense!

    Do you know of any eggs laid around the end of May and chicks which successfully fledged?

    We know the chicks at Threave in 2012 were late but we do not really know when the eggs  were laid as there is not a cam on that nest. 

  • Rothiemurchus was the oldest chick of one of the latest broods ever ringed by Roy Dennis.  Ringed on Aug 10th, fledged Aug 18th, migrated Sep 6th.  Allowing 38 days for hatching and 53 days to fledging that would give a laying date of c. May 20th,  hatching on June 27th and migration at 71 days.

    Hilary J

  • In 2012 the first Threave chick fledged on 25th August & the second had fledged by the 30th, the Father & young Ospreys were last seen together on the nest on 6th Oct 2012.

    I also suspect that with milder weather Ospreys could potentially migrate later from Rutland than a more northern or Scottish nest

  • The very latest brood that we have exact statistics for is Dyfi 2013

    There egg #1 was laid on 22 May and egg #2 on May 25

  • Unknown said:

    In 2012 the first Threave chick fledged on 25th August & the second had fledged by the 30th, the Father & young Ospreys were last seen together on the nest on 6th Oct 2012.

    I also suspect that with milder weather Ospreys could potentially migrate later from Rutland than a more northern or Scottish nest

    It does seem that this brood was running a week behind the Dyfi 2013 brood. 

  • HilaryJ said:

    Rothiemurchus was the oldest chick of one of the latest broods ever ringed by Roy Dennis.  Ringed on Aug 10th, fledged Aug 18th, migrated Sep 6th.  Allowing 38 days for hatching and 53 days to fledging that would give a laying date of c. May 20th,  hatching on June 27th and migration at 71 days.

    Rothiemurchus must have migrated very early. Some of Logie's chicks migrated very early but they did not get to Africa. 

  • Hazel b said:

    In 2012 the first Threave chick fledged on 25th August & the second had fledged by the 30th, the Father & young Ospreys were last seen together on the nest on 6th Oct 2012.

    I also suspect that with milder weather Ospreys could potentially migrate later from Rutland than a more northern or Scottish nest

    It does seem that this brood was running a week behind the Dyfi 2013 brood. 

    [/quote]Threave blog from 9/8/12: "The birds showed signs that eggs had been laid around the 30/31 May. We believe the chicks hatched on the 5th July."

    So fits in with your above dates for latest egg laying dates.

  • I would think that if 30(05) and 28(10) at Rutland do produce eggs they're going to be running to a similar timeline to Dyfi in 2013.  No worries there.

    Our herring gulls are red listed birds.  Think about that the next time you hear some flaming idiot calling for a cull of them.

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