Saturday 17 May 2014

BirdBoxPiCam2014: the box falls silent

It always seems strange to me, once the blue or great tits have left the nest, that the nest falls silent.

After 10 weeks of activity inside the nest box, 10 weeks of checking video recordings & watching "live" when we get the chance, the last chick leaves, and the screen displays a static view of moss, dried grass and dog hair.

And the view inside the box will probably remain largely unchanged (apart from the addition of more cobwebs), until next spring.

Since watching our first bird drop down into a nest box in 2009, we've been hooked. That first low resolution, monochrome image of a blue tit was enough to drive me to buy a second, then a third camera. Each year we've changed or enhanced our equipment and setup.

Some years have been more successful than others. However, the combination of technology and garden birds means there is no guaranty of success. But if you don't make an effort, you wont see anything.

The 2014 season has been notable for the use of the RaspberryPi. This has resulted in much better image quality, and the ability to run a battery powered wireless system. But one thing is missing now, that we enjoyed back in 2009; audio.

So with each new season we make changes, mostly for the better, and of course there will still be plenty to do this winter in preparation for the spring of 2015.

How the season panned out

On the 1st April I set out a plan based upon a guess that there would be 8 eggs laid and that the chicks would take 20 days to fledge. But 10 eggs were laid, and there were a few other dramas along the way.

My prediction, and how things panned out.

When it was time to go, the first chick to leave seemed to be tormented by the need to get out, and the desire to remain in the safety of the box. The second chick seems stunned to find itself all alone, and remains frozen to the spot until mum arrives. Mum still feels the need to stick her head into the nest cup and root around for bugs (a bit like running the hoover over the carpet just before leaving the house for a 2 week holiday!). This sequence took just 4 minutes, which I've edited down to 1m38s.

I missed the departure by just 15 minutes. I'd been sitting a few metres from the nest drinking tea under the pergola and watching the chicks on my laptop until 2pm. The female arrived and kept giving an alarm call, although I didn't think I was too close. I noticed the chicks move away from the entrance and retreat to the relative safety of the nest cup when they heard this call.

This commotion eventually set the blue tits off, despite their nest being a further 15m away.

I tried to get a glimpse of the chicks late afternoon yesterday, but they seemed to be nicely hidden in dense cover.

The final box "visits" graph looks like this:-

What do you make of this?

I really don't think we can deduce very much from this data. I can't see any link with weather conditions, apart from a short intense rain storm on one day. Garden birds now have the benefit of seed feeders, so the daily feed rate can peak just because the adults choose to draw on the resources that we supply. And this year both great tits and blue tits seem to be using our bird feeders much more for feeding their chicks than we have noticed in previous years.

In 2009, 10 & 11 the blue tits appeared to draw heavily on the abundant supply of green caterpillars found mostly on our hazel tree. Perhaps there is a shortage this year?

It would be interesting to gather data from a nest box that is located in a more natural environment, miles away from any man-made food source.

Maybe one day we will be able to stick a camera to the parents forehead and see where they are going. See what problems they encounter, or what distracts them from their primary task. And see why they sometimes feed their young at a high rate, while at other times they seem to slow down. In the meantime I'll just keep collecting this data, because I can.

Other species

The blue tit family are now extremely noisy. They are in a badly built nest box that I made and put up in 2000/2001. It has been occupied many times by coal tits and blue tits, so may be a good site for a wireless box next year.

This old house...

The last robin chick seems to have now disappeared. The adults began to chase it away about a week ago, and I haven't seen it for at least 5 days. I assume the female is now sitting on the next batch of eggs, but they are not using the "flower-pot" nest this time.

I've just this morning noticed a robin going into the ivy where my 2 camera robin box is located, so I need get this system up and running again.

How the RaspberryPi system performed

Being able to modify the software on the nestbox RaspberryPi remotely, was a big advantage to me. Most importantly it allowed me to enhance the methods for recording video.

It the early stages, when birds are making the occasional visit to check out the box, Kenneth Larvsen's motion detection program is a very useful tool. It allows me to review a limited amount of video for signs of activity in association with the box event count (e.g. if motion triggers recording due simply to light levels in the box, while the box counter is incrementing, you can deduce that there is a bird hanging on the outside, poking its head into the hole). But once the chicks hatch, motion is less useful because it will tend to trigger recording most of the time. However, you never know what may happen when you are not watching the screen, so motion may still be a good default mode.

An alternative may be to record video for a period of time (say 30 seconds) whenever the entrance sensor is triggered. This may give unwanted video each time a bird leaves the nest, unless you are using a system like this.

A better option may be to record video when the entrance sensor is triggered AND there are changes in the video.

During the final days before the chicks left the nest, I added a timed recording mode which simply captured a still image followed by 5 minutes of video, repeating this sequence through the day. This creates a lot of video, but after reviewing the stills, most of these files are just deleted if nothing significant has happened. The cost of memory devices continues to fall, so next year a 32GB SD card will probably be as cheap as a 16GB card was last year.

"It just kept growing". My Gambas generated controller interface.

I understand that creating an RTSP stream is more efficient than HTTP, so that's what I've been using. I'd like to stream a larger (higher resolution) image but would need a faster network. Even the current resolution (640x480) can result in image break-up from time to time.

If this could be more reliable, I could consider making all recordings remotely (as per my original plan). This would make life easier, as the live stream would always be available, and all video files could be stored on a large drive attached to my garage server.

Some ideas for 2015

I haven't thought through much of this, but I'm considering installing up to 3 boxes next year. Maybe some combination of the following:-
2 x wireless tit boxes
starling box?
ethernet robin box
Other ideas:-
audio? It would be interesting to record sounds both inside & outside the box. I'd like to discover/confirm whether the adults determine when the chicks start to leave the nest, or whether its the first chick out that triggers the process. We've seen the adults try to call/temp chicks out in the past, but only noticed this after the first has left.
Motion detection using Raspivid
Garage server: replace with RaspberryPi + RTC + analogue video capture


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