Linnets require seeds throughout the year, and they frequent areas where they can find lots of such food. Typical areas for Linnets include rotational set-aside, winter stubbles, root crops and break crops. Break crops are secondary crops grown to interrupt the repeated sowing of cereals as part of crop rotation. Oil-seed rape and associated broad-leaved weeds provide ideal food for Linnet chicks in the spring with Linnets one of the few species to feed their nestlings entirely on seed. Linnets need thick hedgerows and scrub for nesting but will also use bramble areas on grassland, marginal land and waste ground.
Where can Linnets find all of these things on modern farmland? The answer is that it is becoming increasingly difficult for Linnets to find those things in order to maintain their population. The graph shows the decline in the population of Linnets between 1996 and 2014. Combined figures from the BTO Common Bird Census and BTO Breeding Bird Survey. This is a pretty disastrous fall in numbers for yet another farmland bird.
With the above in mind I met up with Andy for another ringing session at a set-aside plot at Cockerham where we hoped we might catch and ring more Linnets and so collect more data for the BTO. The morning was fine, perhaps too fine with sun on the nets but at least very little wind.
We caught steadily but slowly with a four hour session producing 18 Linnets and 1 Reed Bunting. This increased out Linnet catch to over fifty in just two visits with no recaptures. Once again juveniles/first autumn birds dominated with just 3 adults and 15 juvenile/first years.
Male Linnets are marginally bigger than females as can be seen from the figures above. The wing length of the UK race of Linnet Linaria cannabina varies between 76-85mm (Birds of The Western Palearctic) which serves as a check on our sexing technique of studying the 7-9th primary feathers to separate male and female. We are finding that anything greater than 81mm confirms a male, whereas a measurement below 80mm confirms a female.
Studying the tail is a very reliable way to age Linnets at the moment. The tail feathers of a juvenile/first autumn have a mostly pointed shape, particularly the outermost unmoulted ones. By October an adult Linnet has completely moulted and replaced its tail feathers whereby the resultant shape is both more rounded and less worn than those of a juvenile/first year Linnet. This holds true for many finches and other species at this time of year where adults and juveniles have differing moult sequences. This is not entirely fool proof as a bird might lose all or some of its tail feathers at any time, and ringers must be mindful of that possibility.
Today’s Reed Bunting proved to be a first autumn female.
Our ringing was carried out to a three hour overhead procession of Pink-footed Geese leaving Pilling Marsh for their daytime feeding areas. Several thousand flew south between 0700 and 1000, with many flocks of several hundred birds among the hordes that passed over.
Otherwise – a few tree Sparrows and Skylarks plus the now regular Sparrowhawk. On the way back I stopped at Pilling Marsh to see 28 Little Egret and 2 Buzzard.
Linking today to Eileen's Saturday Blog.