27 Jun 2013

Growth bars amongst other things

Another sign that many of our commoner birds have suffered in the unsettled spring was this juvenile Great Tit caught in the garden showing growth bars in the tail. Many of the other juveniles are showing something similar but this was the most pronounced. Growth bars are like tree
rings - you can tell what's happening during the growth period by looking at the presence of the growth bars. During times of food stress the feathers don't grow as well as all the energy is put into keeping the vital organs supplied with food.  A lot of the juveniles are in poor condition with poor quality feathers although their fat scores are pretty good as they're stocking up on the food I'm providing.

Some good news on the juvenile front though. The local Goldfinches and Chaffinches have taken advantage of the spell of warm weather and have fledged young who are now flocking to the feeders. A pair of Robins have also successfully fledged at least one young nearby as I caught this little beauty as well.

Although the Magpie was caught predating the Robins nest in our front garden my daily attempts at keeping them at bay with a selection of stones has proved successful and the remaining eggs have hatched. The only problem is I've run out of gravel by the front door!

I spent a cracking evening up on the River Lune midweek with guys from the North (see here)Lancs Ringing Group ring Sandmartins as part of a long term study they are doing on adult survival rates. First bird  I was given to process had a French ringing scheme ring on! Their 3rd French control this year. I've never ringed at a Sandmartin colony before and was intrigued to learn that juveniles won't leave the natal colony until their wings have grown to at least a certain size and that once they move away they're regularly caught at other nearby colonies before doing the teenage thing and doing a grand tour of the UK before migrating to Africa. Sand martins are lovely little birds but one of the undoubted highlights of the night was watching a young otter at close range.

Heart breaking news from Harris though where a White-throated Needletail put on a fantastic display for a couple of days before colliding wit ha wind turbine and being picked up dead. We'd arranged to go for it today and there was a few disbelieving tweets and texts going around last night before the photographs of the bird in the hand were posted. The bird had survived a journey of thousands of miles to be killed by a supposedly green energy source.

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