The Barn Owl Detectives

Last weekend we were swooped upon by an enthusiastic group of mammal detectives, who couldn’t wait to find out what was on the menu in our Owl Pellet Analysis workshop. 

Each armed with a forensic tool kit of tray, gloves, tweezers and tooth-brush, they set to work to discover what the barn owls at Denmark Farm have been eating.    

barn owl pellet analysis

As well as being an fascinating way to spend a few hours, owl pellet analysis can also generate useful data on the birds’ diet, and provide information on the distribution of small mammals. Many bird species produce pellets including owls, raptors, gulls and even sparrows. The prey is swallowed whole, and the pellet containing the indigestible parts of the food such as the fur and bones is then regurgitated. Barn owls provide a particularly good source of pellets as they tend to drop them under their roost sites (a licence is needed to enter when the roost is in use), but pellets can also be found on or below fence-posts and walls where a bird has perched to feed – so it’s worth looking for them when you’re out for a walk.

barnowl pellet analysis

Examining owl pellet remains in the microscope

Our detective session began with a presentation on how to identify mammals from their jaw bones and teeth. The group was then let loose with a variety of barn owl pellets, donated by local roost owners, as well as a pellets from our own barn owls at Denmark Farm. Participants also brought their own pellets to identify – including tawny owl and buzzard, and their efforts were rewarded by finding a lizard leg in the buzzard pellet.   Microscopes were on-hand to give close-up views of our finds: 


Common shrew skull, with diagnostic red-tipped teeth








We spent time comparing notes and specimens, and puzzling over the numbers of tooth roots in each jaw bones, searching for the elusive 5-rooted tooth of a harvest mouse, and the 4-molared jaw of a dormouse.  Records for both harvest mouse and dormouse are scarce in Wales, so finding a skull could provide valuable information about their distribution. We didn’t find any this time, but did find other small mammal remains including field voles and common shrew with their distinctive red-tipped teeth, as well as identifying the weird and wonderful selection of other bones. One young participant even re-assembled the bones from her pellet into the skeleton of a field vole.

 Partial field vole skeleton, reassembled from a barn owl pellet 

Our detective work kept us absorbed all morning. As one participant told us ‘We’ve collected pellets before but never fully dissected them. It was interesting to devote time to this and concentrate. It is hard to do that at home. Great to see the kids so absorbed.”

If you would like to give this a go at home, then a downloadable guide is available on the RSPB website, and further information and resources on the Barn Owl Trust website.

If you’d like to discover more about small mammals there is a British Mammals: Gnawers, Nibblers and Insect Crunchers three-day course coming up in May 2018 at Denmark Farm. There are also many other events on our website for keen nature lovers and ecologists

Grateful thanks go to Aline Denton and Chloe Griffiths for facilitating this workshop.

Photos taken by Aline Denton, Chloe Griffiths and Jon Sayer.

2 thoughts on “The Barn Owl Detectives”

  1. Anne

    Thank-you Choose and Aline. It was a good way to spend a rainy Saturday! Maybe a ‘nature detective’s day would be good sometime? Looking for animal tracks and signs outside, and a bit of indoor investigation like owl pellets in case of soggy weather?

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