Saturday 19 January 2019

BirdBox 2019: early interest ( hog & bats update)

Seeing small garden birds showing an interest in our bird boxes is a reminder that the nest box season will soon be upon us.

There is a long run in, a couple of months of building, egg laying and chick rearing, and then its all over for another year.

So make sure you are ready by putting up any new boxes now!

Blue tits have certainly been showing interest in nesting site in southern England since Christmas.

raspberry pi, nest box, blue tit, great tit
This lone blue tit needs a mate!

There is nothing very unusual about this, as they can spend months faffing around, going in and out, tapping on the outside, and showing their girl-friends around until they finally start building a nest in April.

But a couple of days ago I saw a pair of great tits also go into the box above and spend quite a bit of time checking it out. In our experience, the great tits often just rock up at the end of March/beginning of April and start building pretty much straight away.

Maybe these are the same pair that evicted the blue tits last year.

this magnificent male great tit will be tough competition for any male blue tit

Either way, we may be in for another interesting season, especially as we still have large mixed tit flocks raiding our bird feeders (e.g. coal, blue, marsh, great and long-tail tits).

A local male sparrowhawk has perfected a surprise attack where he flies low & fast up a neighbours garden, over our garage roof and down onto the feeders. But his success rate may be as low as 1 in 10, and we haven't noticed him for the last 2 weeks, so maybe he hasn't survived.

However, just like last year, I don't intend to do any technical work on the bird box system. If it powers up and runs OK when I eventually hook up the battery, fine. If not, we are just going to have to be content with watching from the outside.

Hedgehogs & Bats

We caught site of a/the hedgehog a few nights ago when it stepped in front of the camera watching rat bait.

Hog looking for a snack on a cold night

I still don't know where it is hibernating. Its certainly not using our expensive hog house, but its looking to be in good condition.

I have been running my Ultramic/Pi bat logger on most dry days during this month, but have not recorded a single bat call. You can call me an old skeptic, but I'm beginning to wonder about the validity of the winter data produced by the monitors in the Queen Elizabeth Olympic Park.

Quite a few of the 13 detectors currently still on line seem to count bats every night, irrespective of whether conditions are dry, very wet or very cold. And many of the counts occur during twilight.

My system also captures a few recordings during those twilight hours, mostly in the morning...

The 'white waves' are the 3rd harmonics between 20-25kHz

...but these are generally due to the strong third harmonic in bird song. I guess some blackbird is singing just above 7kHz and creating harmonics in the 21-25kHz band!

So the question is, how good are the London bat monitors at determining genuine bat calls from regular bird song?

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