So, a few years ago I was drinking with a group of birders, we used to always meet up on Christmas Eve in the Westend of London for drink and talk mostly birds all night. Now we are all middle aged and spread across the world, so these gatherings rarely happen. So Sam was explaining to me that someone had carried out some breeding bird surveys in the rainforest where he lives in Costa Rica. They had stated there were few birds present of any consequence. It turned out they visited the site in the middle of the day and unsurprisingly didn’t find many birds. Sam went there at the correct time (pre- dawn) and picked up loads of birds. So now this is a familiar story to me, people surveying at non-peak times of the day. Having birded a patch for many a year I know that birds sing early in the morning. During my early years of carrying out breeding bird surveys I kept moving forward my start time from sunrise to 1 to 1.5 hours before sunrise. After a few times of arriving on site to find the birds already singing, you think well I should be here earlier to catch the start. That way you catch all the early singing birds plus the activity is more significant. In the old days, I would be asked to carry out just one or two breeding surveys on a site. Now the minimum I do is four. So I spread these over the breeding season to give me a good idea of what is present and adjust it for any specific species I may find or think is present.
So what research am I carrying out now, well, I want to know when is the best time to start surveying for breeding birds? Which months are peak for which species and what are the relevant times of the day? Often I am told you need to start no later than one hour after sunrise and I am told that guidelines state this. To me, you’ll miss out on loads of breeding birds such as Song Thrushes which are one of the earliest singing species during the dawn chorus. Now, how do I prove my theory, that you need to be out early?
So my methodology is simple:
start an hour before dawn
- walk 500m in a straight line counting all the singing birds present
- repeat every half an hour along the same route for six hours, only walking in one direction
- analyse the data to see peak times for singing during the year per month?
- analyse the data on a half hourly basis
- analyse the data per family per half hour per month
- analyse the data per species per half hour per month
- all surveys to be carried out in ideal weather conditions, sunny and windless days. No
surveys to be completed on days of heavy rain and strong winds - this reduces the
territorial behaviour
- survey once a month a for year for a complete picture
Originally I was going to do this every hour but I soon realised this should be every half an hour. I would need to start before anything starts singing and finish when it all slows down. This would show the peak periods for all birds plus the species that are present.
So what I am showing here? This chart above shows you the total birds singing for an hour before sunrise (-1) to four and half hours afterwards (4.5). Here you see that rapid peak in vocalisation of the territorial birds and that the first four surveys after sunrise accounted for 44% of all singing birds. Extend that to the first eight and you get 77%. What this does not show is any repeat offenders being counted more than once. So one Song Thrush that sang from sunrise through to the fifth survey would be recorded every time. This is early in the breeding season and reflects they have just started the process towards the breeding season but have not yet settled down for business. This was true on the day a few bonded pairs were obvious such as Great Spotted Woodpeckers, Treecreepers and Stock Doves but the not the majority of the birds present.
This next chart shows the split per family. The first leap (the orange line) are Thrushes, they really peak early and then tail off. Then you get a peak with Tit species. Then comes woodpeckers and Nuthatches with the last family, Finches. So with more species singing I will gain a clearer picture of when they peak and in which months.
Here’s something I didn’t notice before. In the wood the Song Thrush started to sing at sunrise, prior to this the only Song Thrush I could hear and there was only one, was from outside of the wood in an urban street. Do some Song Thrush sing like Robins near street lights? I only heard one Blackbird and that was at sunrise but outside of my survey area.
So what I have learnt? Well it lasted longer than I expected, so future surveys will be longer depending on the activity. Also that I could do with this being repeated in different habitats as well. There is only me carrying out this research and I have a limited capacity to carry out this work. Just another 11 months of pre dawn starts for me....