Back to blog listings

It’s all grow, grow, grow on the nest this week

Posted: Friday 7th June 2019 by Kim MWT

MWT chick fight 2019MWT chick fight 2019

As the Bobs enter their second week we are starting to see some new behaviours as the dynamics of this growing family develop.

Growth Rates

Today the Bobs are 12, 11 and 9 days old. They are growing rapidly and changing daily. Monty is continuing to provide a steady supply of fish and Telyn is feeding all three chicks efficiently and with precision. It will take around 35 days for each chick to reach full size and to weigh in at 1400g – 1700g.

A newly hatched osprey chick weighs between 50g – 60g, they double their hatching weight in the first week of feeding, then need to gain around 40g a day to reach their full size. Their protein packed diet helps them to grow quickly.

Contented Bobs take a snooze

MWT sleeping chicks


At the moment it is relatively easy to distinguish the Bobs from each other as they are beginning to develop their ‘second down’ this is the set of fluffy feathers they will have for the next couple of weeks.

The older chicks are beginning to develop new feathers

MWT chick development

The down helps to keep the chicks warm as they begin to regulate their own body temperatures. This becomes increasingly important as they grow and Telyn is less able to brood them as effectively.

Telyn is less able to cover the chicks fully as they grow

MWT chicks under Telyn

Sibling rivalry

It is not just squeezing in under their mother that becomes more of a challenge as the Bobs grow. As they get bigger they also start to exert their presence on their siblings. It is very rare for ospreys to exhibit siblicide or cannibalism but they can display aggression towards each other.

Bobs one and two are very close in size and aggression. They have already begun to squabble, for now Bobby Bach is keeping out of these challenges. 


For the next few weeks Monty will need to continue to provide a constant supply of fish to ensure the chicks continue to grow steadily. You may already have noticed that he is bringing more whole live fish in to the nest than when the chicks were very small. As the chicks grow in size there is less risk to them from a tail-flip or a flounder-flap! However, Telyn is still quick to handle the wriggly ones swiftly to ensure no damage is done.

All three Bobs feast on a flounder

MWT Flounder feast


What goes in to an osprey chick must at some point come out again!! A bird’s excretion system differs from our own in a number of ways. Most birds have only one multipurpose orifice, called a cloaca, which is used for getting rid of waste, laying eggs and reproducing. It is the same in both males and females and is not visible on the outside of the bird.

With only one hole available birds expel a mixture of both poop and pee at the same time. Just like us the pee part of their waste comes from the kidneys, however, while ours is urea that dissolves in water to make urine, birds produce uric acid to save water – especially important when all your fluid comes from your food. 

The Bobs are now mobile enough to manoeuvre their rear ends towards the outside of the nest for ablutions but they have not yet learned the importance of checking the wind direction before pooping!!! Poor Telyn quite literally got an eyeful of poop earlier this week!!!

Telyn finds herself downwind!

MWT Telyn gets a poop in the eye

Read Kim MWT's latest blog entries.