Mixed fortunes

Unfortunately I didn't get round to posting our Belvide results from last Saturday but in truth it wasn't that good with only 35 new birds ringed --although we did have a high spot when one of the adult reed warblers we caught was found to be wearing a French ring. It was probably ringed as part of the extensive estuarine ringing scheme mentioned in my last post. More details later.
Fast forward to this morning and perfect weather conditions for a ringing session. The first net round suggested we were in a for a session with more ringers than birds but things soon picked up and we ended the morning with a very respectable 59 new birds and a dozen or so retraps from previous years.
One of the benefits of a scheme like this is that with pretty consistent ringing effort year on year we can get a good idea of population dynamics from our results. Over recent years our most numerous ringed species has been sedge warbler with many juveniles indicating successful breeding and migrants regularly calling in to feed up. It's a little early for migration ( not too long to go though!!) but the ratio of adult birds to juveniles especially at this time of year, obviously gives us a good indication of breeding success. Of the 59 birds caught today 22 were reed warblers and only 9 were sedge warblers. Furthermore 16 of the reed warblers were juveniles indicating that they seem to have survived the cold wet spell better than the sedge warblers. This may be because the latter usually nest nearer the ground than reed warblers and may have been washed out by rising water levels. Fortunately there is still time ( with good weather and falling water levels) for these birds to nest again so we hope to see more juvenile sedge warblers in the coming months.
One particularly interesting feature of breeding birds at this time of year is the way female birds in particular develop what is called a 'brood patch'. This is an area on the belly where the feathers are shed to create a patch of bare skin which, when placed against the eggs or very young chicks keeps them warm. The bare skin also becomes engorged with a rich blood supply to increase its warming capacity. Once the eggs hatch and the chicks are growing the brood patch looses its rich blood supply but the skin is left wrinkled from the previous engorged stretching--as you can see quite clearly below on a bird from this morning:-