Wednesday 23 April 2014

BirdBoxPiCam2014: Chicks in the nest

Things are really kicking off now, as chicks have started to hatch in the great tit nest box.

Dad brings in most of the food, as mum still has the job of keeping chicks and remaining eggs warm.

This is generally seen as the final, and most interesting stage of the process.

By 6am yesterday morning (Tuesday 22nd) the first chick had broken free of its egg. As I was out of the house for most of the day, I am unable to say how many of its siblings also hatched.

But by 6am this morning I could only count 3 eggs, and I'm now sure with have 7 chicks in the nest. It remains to be seen how many of the remaining 3 make it!

It is difficult to estimate the size of the chicks, as objects which are twice the distance from the lens appear one quarter of the size. These chicks are sunk well into the nest cup.

There were pieces of egg shell scattered around the nest this morning. Shell is generally either eaten or carried some distance from the nest, so as not to attract predators. The female slowing munched her way through each piece, taking over an hour or so, as if pacing herself (like me eating broccoli).

The adult male is doing a good job so far collecting food for the chicks and his wife.

In this clip he brings back some kind of insect which has been partly flattened. It looks too big for the chicks to swallow, but it eventually disappears.

In some of David's early observations (see his diary for year 2000), he witnessed meal worms being prepared before being offered to blue tit chicks. By his account, the adult appeared to remove the head and guts. So I wonder if that is what has been done by our male great tit.

Data from the RaspberryPi shows that the number of round trips made by the adults ("in and out", or "out and in" to the box) is ramping up. It was about 120 yesterday, but for this morning (up to 12noon) its already 70. This time last week it was about 30 for the whole day.

Tracking Progress

Here is the great tit plan with updated progress tracker.

Technical Stuff

The videos above have a container/wrapper added to the H264 stream using MP4Box, and have been edited in Avidemux.

Both videos have been cropped on all sides, mainly to reduce the file size. The chicks video has also been sharpened a little. But once again I have to say that the quality of the web video is degraded quite a bit compared to my local copy.

I now have two 12Ahr batteries which I use alternately. They easily last for 50 hours run time, at which point the loaded voltage falls to around 11.8Volts.

They would probably last about 60 hours, but its not in my interest to let them go flat and dump my RaspberryPi while it might be doing something important.

My "things to do" include:-
  1. modify my VLC capture/record command to also maintain streaming (i.e. view and record at the same time).
  2. Investigate MP4Box: looks like I may be able to run this directly on the RaspberryPi to produce video with an MP4 container format, rather than just an H264 video stream. May also be able to add hard/soft subtitles, so I can add the same kind of info as shown on the Motion stream
  3. Build a second RaspberryPi camera system to capture 90fps video outside the box, possibly incorporating my PIR. This would only be used on dry days to capture birds arriving/departing (adults & chicks).


  1. Cool, great footage there. On point number 3, would it be possible to do that all on the one Pi?, e.g. use PIR as a trigger, or entry hole IR beam to capture exits? Maybe a random thought but what about running a high fps recording to some sort of memory buffer which is dumped to SD card in the event some sort of sensor is triggered?
    I found 30cm camera cables here which could be helpful:

    1. Apparently you cannot use 2 RaspiCams on one Pi, but some people have successfully used 1 RaspiCam + 1 USB cam (e.g.

      As there are only a few weeks left for our great tit family, I'm going to try making a free-standing 2nd camera which I can then use around the garden (e.g. at the feeders). I've got some bits on order, so hope to make a start this weekend.

      Did your Python loop delay change reduce cpu temperature?