Vital statistics

When the Rutland osprey chicks are ringed, the trained staff seize the opportunity to take measurements of the birds and weigh them while they are in the hand. This furthers our understanding of osprey ecology and helps indicate the sex of the birds.

As well as being heavier than males, females are generally the chunkier of the sexes. Females tend to have thicker bills, legs and larger heads and this is usually noticeable as early as around five weeks old when the chicks are ringed. It is worth remembering, however, that the female chick 057 is by far the youngest of the brood (having hatched six days later than the first two chicks and four days after the third), therefore the sexual dimorphism usually seen in ospreys isn’t so marked and some of her biometrics are actually a little smaller than her male siblings.

Biometric measurements of Manton Bay chicks 21-06-2019

BTO ring no.Colour ring no.SexBill to cere (mm)Bill depth (mm)Head inc. bill (mm)Tarsus length (mm)Tarsus thickness (mm)Wing length (mm)Weight (g)
1380 101054F30.119.17960153481620
1380 102055M26.918.77857.3143441400
1380 103056M26.617.477.95814.93001440
1380 104057F25188063.3162831620

The ringing of the osprey chicks is conducted as quietly and efficiently as possible by our trained ringer, in order to keep stress to the osprey chicks and the adult birds (as well as Wildlife Trust staff undertaking the work) to a minimum. The welfare of the birds comes first and is prioritised above all else.

7 responses to “Vital statistics”

  1. Lucy Whitrow

    Great to have an update on the chicks. Why does Maya not have rings? How can you tell it is her returning?
    It is amazing that she & 33 have successfully raised 4 chicks. When do you expect them to take their first flight. Will the parents wait until the youngest is ready for the long journey before they all set off south?
    I am so enjoying the webcam. Thanks to all those involved.

  2. Michael Tennant Grundy

    Very interesting information on the sexing & ringing of osprey chicks. Thank you.

  3. Michael Simmonds

    Thank you Rebecca. 057 certainly seems to have matched the criteria for weight!

  4. Robert Dunkley

    Have any of Maya and 33’s chicks from previous years been recorded/seen at Rutland or UK? I understand that it may 3 or 4 years before young ospreys make the return migration to Europe.

  5. Bill Hunt

    5 weeks in the life of an osprey makes for amazing changes! Almost in the blink of an eye the eagerly awaited hatching of eggs suddenly becomes a nest full of beautiful raptors. We are privileged to watch this lifecycle year after year and with the informative blogs we are blessed by a commentary to keep us fully up to date. Thank you!