Sunday, 24 December 2017

Whose been eating my birds?

The natural world is something I find incredibly relaxing and fascinating and sometimes it is easy to forget that although I get great solace in watching birds and animals they themselves are focused on eating to survive and avoiding getting eaten themselves.

One should avoid becoming oversensitive to the 'cruelty' of nature. In fact, cruelty is the wrong word, a fox isn't cruel catching a rabbit to eat. Cruelty should be replaced by reality. Predator/Prey relations are fascinating things, they are one of the prime movers in the evolution of species and the dynamics involved create amazing adaptations and behaviours.

Occasionally on my patch, I encounter a dead animal. It is surprisingly rare. This is because nature has the best recyclers in the world. If an individual isn't devoured in its entirety then a host of scavengers and decomposition can cause any carcass to disappear in an amazingly short time.

Today I found the remains of a black-headed gull. There seagulls frequent the fields in the winter sometimes in quite large flocks especially directly after the fields are ploughed. In December a few birds still visit the fields and it is one of those that succumbed to predation.

Nearly all the 'meat' had been removed by the time I found the bird lying in grassland adjacent to the crop field. Many of the feathers had been removed but there did not seem to be any wings present. Many experts are able to identify the predator from such remains and I am going to have a stab at exploring this myself.

The crime scene consisted of a single adult gull. Both wings and all primaries were missing. Both legs and skull were intact. It was surrounded by a mass of feathers including down and secondaries.
Each feather seemed to have been plucked rather than bitten. Most mammals bite through the feathers when getting to the flesh whilst birds like the sparrowhawk pluck them out, leaving the shaft of the feather intact.

The key suspects are Fox, Buzzard, Sparrowhawk, Peregrine, Kestrel. Let's examine each in turn.
The intact feathers and the fact that a fox would find it difficult to sneak up on a gull in the field seems to rule it out although as much a scavenger as a predator it could have moved the carcass.

Buzzards certainly have a wide and varied diet but are they agile enough to catch a gull? No, although an injured or sick one would definitely be fair game. Kestrels I think would be too small. They are fast and agile but suspect they wouldn't have the strength to take one down.

This leaves us with both a Peregrine or a Sparrowhawk. Both are viable candidates and occur on my patch. Of the two the Sparrowhawk is more likely as they are much more common on the site. They are ambush predators and could easily take a gull. Peregrines likewise have speed and strength on their side able to dive down and snatch birds from the sky.

Without forensics or witnesses to question I will never know the truth but I can narrow the field to these two raptors, both impressive predators in their own rights. The gull's gloomy end may well be bad for the gull but it means that the predator and all the decomposers can live on. In the words of Elton John - Its the circle of life.

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