I took part in there BTO Early Bird Survey this morning. The purpose of the survey is to build on observations from the Shortest Day Survey, and will investigate what effect, if any, light and heat pollution have on the feeding patterns of birds during a cold winter’s morning. The BTO Shortest Day Survey took place on 21st December 2004 and was promoted by BBC Radio 4 via the Today Programme. Some 5,460 responses were received from participants and these were used to determine patterns in the arrival of birds at garden feeders. The pattern of arrival, on average, was:
The BTO researchers then examined the arrival patterns in relation to a number of factors, including relative eye size and local habitat, in order to establish whether there was anything that determined when birds first arrived at feeding stations. They found that there was a negative correlation between eye size and time of arrival at garden feeders across species, and that this relationship remained significant when body mass was taken into account. This suggests that the time at which garden birds begin to forage on winter mornings may be limited by their visual capability at low light intensities.
They also found that birds appeared at garden feeding stations later in the morning in urban areas than in rural areas during winter. This supports the hypothesis that heat pollution may reduce overnight energy costs in small birds in urban areas, thereby reducing the urgency for them to 'refuel' first thing in the morning. Further information on the Shortest Day Survey can be found on the BTO report on-line at http://www.bto.org/volunteer-surveys/gbw/about/background/projects/shortest-day-survey
Preparation for this mornings observation involved identifying the number of street lamps within a 50m radius of garden, so using a great website at http://www.freemaptools.com/radius-around-point.htm, I was able to draw a radius around the house. This gave me a total of 4. Two near the back garden where the feeders are, and two in the front of the house. I also had to measure the minimum and maximum temperature overnight.
So what happened this morning then. Well I made myself comfortable at the kitchen window while still dark and about 45 minutes before the scheduled sunrise, as predicted by the BBC weather page. Thus armed with a cup of tea (absolutely essential), the binoculars (not so essential, as the feeders are quite close) I was ready! It was a dark morning after the heavy rain last night, and because it was still heavily overcast. A male blackbird was the first to arrive, almost as soon as it was possible to see the feeders, and way before the scheduled sunrise, followed by a robin. The collared doves and jackdaws paid only a cursory visit, and seemed more intent on sitting the the Rowan tree "having a good chat" with their respective partner. All of the other smaller birds made fleeting visits to the feeders, primarily because the the robin patrolling the immediate area and chasing off anything smaller than itself. The results from this survey can be found on BTO website http://www.bto.org/volunteer-surveys/gbw/about/background/projects/early-bird-survey
I had a quick look at the BTO website to compare my observation with the others that had been submitted by al the other citizen scientists involved. Like my observation, the blackbird and robin were the first to appear in almost all the observations submitted. However, the smaller birds arrived earlier to the feeders than in my garden. I wonder if the aggressive robin is having any influence on this. I think I'll follow this up with other observations later in the year.