What is a bird pellet?
A bird pellet is a ball of matted fur, bones and skulls regurgitated by a bird. Essentially, it contains anything a bird cannot digest. A bird will bring up a pellet most days, sometimes twice a day. It is a necessary process and birds cannot eat whilst they are bringing up a pellet.
Which bird species throw pellets?
A great number of bird species throw pellets including kingfishers, owls, falcons, hawks – even some garden birds like robins.
What is inside a pellet?
What is inside a pellet depends on what the bird has eaten that day. Just one barn owl pellet can contain up to four vole skulls and three common shrew skulls, their fur, and bones. I once found grass inside a short eared owl pellet – evidence that the owl had swallowed its prey whole, which is something they often do to stop kestrels from snatching it off them!
I’ve also found a weasel skull in barn owl pellet. I’ve found leveret bones and frog skulls too. Little owl pellets actually shimmer with the iridescent wings of the beetles they eat, whilst kingfisher pellets are very fine, loose structures made up of fish scales and fine fish bones
How to dissect a bird pellet
It is interesting to dissect pellets to see what the birds are eating. I was very surprised to discover a barn owl had taken a weasel and might not have believed it if I hadn’t seen the weasel skull in its pellet! I recommend soaking pellets in water to help them come apart.
How big are bird pellets?
Pellets can vary in size, depending on the bird coughing it up. Most species seem to be able to bring up relatively big ones. It can be quite alarming watching young chicks spitting out pellets that look too big for their throats, but on the whole they do manage. In my studio I have some, very sharp, bones from a gull I found inside a pellet thrown up by a sea eagle and I did wonder if those bones had stuck they could have hurt. I’ve also got then remains of a goat from an eagle pellet.
Do pellets smell?
Unlike faeces, pellets have not been digested and so they don’t have a smell and don’t carry disease. They can smell a little ‘fusty’ but that’s all.
What role to pellets play inside bird nests
Many birds break up their pellets to line the floor of their nests with. Owls do this, and kingfishers too. Kingfisher nests are deep underground and there is nowhere for their faeces to go and so these broken up pellets do an important job absorbing their poo and keeping the nest clean for the chicks. In fact, a kingfisher will not lay her eggs until she has a soft layer of pellets to lay on.
In the kingfisher nests I have watched it seems to be the female’s job to shred the pellets as soon as they are regurgitated by the male or the chicks. She does this deftly with her sharp beak.
Bird pellet eco-systems
The pellets that fall on the floor of a nest also support other life forms. For instance, as the detritus of owl pellets builds up in an owl nest it will attract insects like flies and spiders which smaller birds then eat. I’ve seen wrens and tree-creepers searching for insects inside owl nests.
Clothes moths and owl pellets
Of particular interest is the white shouldered clothes moth, which lays its eggs inside vole fur. The owl eats the vole then regurgitates a pellet containing larvae which then pupate inside the owl nest. These pupae then sustain other birds over the winter. I have filmed this process after watching a tree creeper ‘eeking’ larvae out from a crevice in the side of one of my owl boxes.
Robert E Fuller