Tuesday, 30 November 2010

Owl pellets

Talking of top predators, a while back, a large bag of smelly owl pellets arrived on my desk with the request, “Can you see what’s in these?” They were large pellets, 70 mm long on average and had arrived from, let’s say, an upland location.
Of the 35 pellets collected over two years (12 in 2009, 23 in 2010), 28 (80%) contained mammal remains, including Rabbits (23), Field Vole (7), Brown Rat (1) and Stoat (1). Eleven pellets (31%) contained bird remains (at least 4 Red Grouse and 1 Pheasant, with 2 probable Pheasants). The mass of loose remains found with the pellets included 3+ Rabbits, 1 Field Vole skull, 2 bird skulls (Red Grouse), 1 bird leg (Pheasant) and many Red Grouse feathers (probably from one bird).

So, in this small sample, Rabbits formed the bulk of the prey in both years, with a smaller percentage of Red Grouse/Pheasants, not a surprise as these were all common in the locality. All the voles came from the 2010 pellets, suggesting a local abundance that year.

The diet of Eagle Owls is known to be wide and varied, but usually reflects the local abundance of suitable (available and economic) mammal and bird prey at any particular time. It is also well known to be very intolerant of ‘minor’ predators within its territory, suppressing their numbers through direct predation. Such behaviour is typical of top predators. Although concern has been voiced about their impact on nesting Hen Harriers, we all know what the main predator of the harrier is!  Personally I’m glad this magnificent bird has regained a toehold in this country. Now, what about the Lynx?; that should sort a few things out.

A photo below of an Eagle Owl pellet deposited on the remains of a Bittern! – taken in Belarus I might add.

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