12th July 2017 - A bunch of Blackcaps

I only managed a 06:30 start at in the top willows at Billinge but I don't think I missed much as a result, at least I hope not. I set three 18m nets under clear blue skies and with only a light breeze blowing from the NE. The catching rate was better than expected for this early in the month and suggests it has been a fairly productive breeding season, especially when compared with the last couple of years. I packed up at 11:00 as the sun was shining on all the nets by then, making them much more visible, and before it got too hot.

The final total of 44 new birds and 2 retraps was mainly comprised of juveniles and included 32 warblers, 17 of which were Blackcaps. The two retraps were an adult male Blackcap that was originally ringed as a juvenile in July 2015 and a juvenile Blackcap that was ringed just over a week ago. The Blackcaps were mainly feeding on raspberries that grow wild near one of the net rides and most of them were caught in that particular net. This raspberry patch usually attracts and holds a good number of locally bred juveniles in July although 17 is more than I usually catch in one session.

Juvenile Blackcap

Juvenile Willow Tit.
Late June and July is the peak period for juvenile dispersal in this species and this is the 3rd to be ringed at the site in the last week.

Juvenile Treecreeper
July is also a time when the young of woodland species disperse and can be encountered well away from their usual habitat. 

There was some interest overhead with the highlight being a Crossbill that called loudly as it flew SW. A Siskin was also heard but not seen and a few Swallows seemed to be heading south. I wasn't in the best place to observe the Swallow movement but small groups appeared to motoring south from time to time; they certainly weren't the feeding flights of the local breeders.

Ringing totals for 12/07/17 (retraps in brackets) were: Blue Tit 2; Great Tit 2; Willow Tit 1; Goldcrest 1; Chiffchaff 5; Willow Warbler 10; Blackcap 15 (2); Treecreeper 1; Wren 1; Goldfinch 6.

Willow Tit wanderings

I mentioned signs of juvenile dispersal in my last post having heard Nuthatches well away from their usual breeding haunts. Well it happened again today but this time it was a juvenile Willow Tit, that I first heard and then caught ,at one of my new ringing sites near Upholland. It was at least a couple of kilometres from the nearest suitable breeding habitat if not further. Now that may not seem far but it is still of interest, to me at least.

Note the wing panel formed by the broader warm buff fringes of the secondaries contrasting with the narrower warm buff fringes of the primaries.

This Willow Tit has a white area on the cutting edge of the upper mandible below the nostril. This is often regarded as a feature of Marsh Tit but is clearly present here.

Willow Tits often show a more extensive and untidy bib as can be seen in this bird.

Most juvenile birds don't disperse any distance until they have undergone their post juvenile moult but both Nuthatches and Willow Tits seem to disperse almost as soon as they become independent from their parents and often before post juvenile moult has even started. It must be important for them to move out of the natal area and find potential wintering/breeding habitat as soon as possible and is likely to be a factor in their survival and future breeding prospects. The Willow Tit I caught today certainly wasn't in suitable habitat to survive year round so its wanderings are far from over.

Willow Tits are also interesting because of their similarity to Marsh Tits, so much so that they were not recognised as a separate species until 1897 which is very recent in ornithological terms. In fact separation of Willow Tit and Marsh Tit remains a current topic for some although the rapid decline of both has removed that concern for many! Now I am not going to give you a complete 'how to' guide here but they do look different even in juvenile plumage and I still think the wing panel is still one of the best and most consistent features for birds in the hand. I have only caught two Marsh Tits compared with what must be hundreds of Willow Tits by now but both Marsh Tits stood out as being that bit different. The second one of my two was in the digital age and is shown below.

 

Juvenile Marsh Tit, Spurn Bird Observatory. Note the even appearance of the wing and the lack of a distinct wing panel compared to the Willow Tit above. This bird was only the 10th record for the observatory.

Other plumage criteria have recently been put forward to help with the separation of Willow Tit and Marsh Tit in the hand and both look like they may hold true, especially with regard to the colouration of the greater coverts (Broughton,R; BTO Ringing News).