Blue Tit versus Coal Tit

One of the fascinations of ringing at a site over the years is that you have an insight into the changes in bird populations. I operate a small broad leaved woodland  feeding station at which ring I ring  on ca 20 occasions each winter and average around 700 birds per winter. This winter has been extraordinary for the numbers of Coal Tits I have caught compared with the number of Blue Tits. This sent me looking back through my records.

I  analyzed the catches in three year periods and worked out the percentage of Coal Tits in the catches the results are as follows-

04-06         24%

07-09         44%

10-12         49%

This means that although up to this winter the numbers of blue tits has been reasonably stable, Coal Tits have increased quite dramatically. In fact for this winter so far for the first time the numbers of Coal Tits have exceeded the number of Blue Tits with 140 Coal Tits and the lowest number of Blue Tits at 96. This gives the highest percentage yet of 60% Coal Tits in the catch.

Why should this be? Firstly, Blue Tits had a very poor breeding season in the cold and wet spring of 2012. Coal Tits obviously did better. But the long term increase in Coal Tits in this area is probably linked to the maturing of the many conifer plantations  to the north of us. I also get the general impression that Coal tits are breeding in larger numbers in mixed and broad-leaved woodlands. They were certainly irrupting last autumn as is so well shown by the ringing totals from another of our sites Heysham B.O. where 474 have been ringed in 2012 compared to just 80 in 2011. It  will be interesting to see what any recoveries we get shows.

John