Pollen Encrustation on Migrant Warblers

I’ve noticed pollen encrustation around the bills of migrant warblers before – especially chiffchaffs, but this morning at Bedfont Lakes I ringed this male blackcap with the most ginormous bright yellow encrustation.

Blackcap with pollen encrustation

Blackcap with pollen encrustation

It made me wonder; where had he come from? What route had he taken to get here? What had he been feeding on to fuel him for his long journey? The majority of this species spend the winter in the Mediterranean before arriving in the UK in spring, so this sticky mass of pollen could have been collected either before it left or any where along it’s journey here. I read about a fascinating study published last year in which pollen encrustations were analysed from 4 different species of warblers, including blackcaps, upon their arrival to the UK. In doing this information about each birds recent foraging beahaviour can be collected and can give an idea as to what areas they may be using to refuel. This is fascinating stuff and the information can be used to identify stopover sites and inform conservation decisions at these sites. I like BirdGuides take on this study referring to these pollen encrustations as ‘time capsules’. There were 19 different types of pollen found – I wonder which ones this giant yellow lump contained?

The long journeys this little delicate looking feathered creatures manage to undergo never cease to amaze me, they are independent and tough beyond all expectations. They arrive here in spring, spend an exasperating amount of time and energy whilst they’re here and then come Autumn they disappear. It’s this enigmatic quality that all birds have that absolutely fascinates me. I just look at this little blackcap, seemingly tiny and delicate in my hand, and wonder ‘what life have you lived?’

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Warblers of Bedfont Lakes

After a fantastic spring and summer of bird ringing at Bedfont Lakes most of the warblers (aside from the resident cetti’s warbler) have left for their long journey to their wintering grounds. Before they leave they have a fair bit of fattening up to do so this is the time when ringers start  noting the weight of these migratory birds and giving each individual a fat and a pectoral muscle score. This is a new learning experience for me and a few weeks back was a great opportunity for me as we caught over 102 birds at Bedfont Lakes South Side between 4 of us (and sadly I had to leave early that day!), including 36 blackcap and 25 whitethroat! This allowed me to compare individuals varying fat and pectoral muscle build up and get to grips with how they feel and look.

I thought this would be a nice time to look at some of the different species of warblers at Bedfont and some of the differences between the juvenile and adult birds. Starting with my favourite – the sedge warbler.

Juvenile sedge warbler

Juvenile sedge warbler

As far as I figure, generally juvenile sedges have more yellowish buff colouring especially on the underparts but from the photo above it is hard to tell if this is indeed a juvenile or an adult (I found it tricky!),  you would need to look closer at the feathers; new, fresh wing and tail feathers and ‘fluffy’ under tail coverts can sometimes be a giveaway, although not always obvious to me. With this species a good clue is the spotty ‘necklace’ most juveniles have – not so much in the one pictured above but you can see here in the one below a line of small dark spots going across the breast.

Juvenile sedge warbler with 'necklace'

Juvenile sedge warbler with ‘necklace’

Really these are beautiful birds, their creamy colouring and dark markings are just fantastic. Definitely have a soft spot for them!

Reed warblers seem to be the most common warbler ringed at the main sight (the Nature Reserve on the North side of the Park). Again new, fresh wing and tail feathers and ‘fluffy’ under tail coverts can indicate a juvenile bird but also in this species the juveniles are usually a more rufous or rusty colour, especially on the upper parts and rump as you can see in this next photo (juvenile on the left).

Juvenile vs adult reed warbler

Juvenile (left) and adult (right) reed warbler comparison

Another indication of age with this species is eye colour – the iris is a grey charcoal colour in their first year then changes to a more olive brown as you can see in this adult bird.

Adult reed warbler

Adult reed warbler

I haven’t managed to get a good photo showing the iris of a juvinile reed warbler but i did get this adorable one of a very newly fledged bird, how cute?! He hasn’t even grown his tail feathers yet!

Juvenile reed warbler

Reed warbler fledgling

Only a little bit more developed is this rather fluffy juvenile cetti’s warbler…. This year was the first record of cetti’s breeding at this site!

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Juvenile cetti’s warbler

Again the juveniles in this species have a darker grey iris as opposed to the brown iris of the adults.

Another common warbler species at bedfont are blackcaps. I mentioned in previous posts (this one and this one) that the juveniles have a duller brown cap, as opposed to the chestnut in the adult females and black in the adult males. The juveniles are are generally more brown and fluffy compared to the adults and have fluffy undertail coverts that are a light brown (or ‘mocha’ as I call it!) colour as opposed to grey in the adults.

Juvenile blackcap undertail coverts

Juvenile blackcap undertail coverts

Blackcap fledgling

Juvenile blackcap

Adult female blackcap

Adult female blackcap

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Upperparts of adult female blackcap

In the last 10 months I have been ringing at Bedfont I haven’t seen many willow warblers but I know the juveniles generally have more yellow underparts and generally brighter yellow colouring all round. This juvenile is a good example, and stunning in in the sunlight!

Juvenile willow warbler

Juvenile willow warbler

Juvenile willow warbler

Juvenile willow warbler

In my experience ringing at Bedfont other warblers that seem to be fairly common are chiffchaffs and whitethroats, the latter only at South Side. Along with willow warblers, other warblers not as common are garden warblers and lesser whitethroats. In fact I think I’ve only seen a handful of adults. In any case, it was a treat as they are both beautiful, smart looking birds – not at all ‘grey and dull’!

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Lesser whitethroat

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Garden warbler

It’s been an amazing spring and summer and now I am looking forward to see what new learning experiences autumn and winter bring!

First Reed Warbler Fledglings at Bedfont

After missing bird ringing at Bedfont Lakes last Sunday (the 15th) I was gutted (for missing it) but at the same time ecstatic to hear that they caught a juvenile Cetti’s warbler, sure evidence that the male Cetti’s we caught back in April and re-trapped several times had indeed found a mate and bred successfully. This is the first record of breeding Cetti’s at this site so we are all chuffed!

This week we also got a good number of juvenile robins, blackcaps, blackbirds and the first reed warbler fledglings of the season, 3 from the same net that were presumed to be from the same brood as they were all at similar stages of development i.e. hadn’t even fully grown their tail feathers yet so perhaps only a day or more old, very sweet!

Juvenile blackbird

Juvenile blackbird

I’ve mentioned before that the juvenile blackcaps look very similar to the adult females but as they develop the black feathers in the caps of the male start to appear (as you can see in the cap of the juvenile male on the right in the photo below) which means we are able to start sexing these young birds.

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Juvenile blackcaps, female (left) and male (right)

We also had to rescue this beautiful Emperor dragonfly from one of the nets, they tend to get caught and then clamp their jaws down and wont let go!

Emperor dragonfly

Emperor dragonfly

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I’m not ringing next week as I’m off to Pembrokeshire on Wednesday for a week of hiking, camping and bird watching! Very excited 🙂

 

Bullfinch at Bedfont

This morning we had a glorious ringing session in the sunshine at the South side of Bedfont Lakes Country Park. A bullfinch was heard a few days before so were hopeful – turns out we were in luck and this beautiful male was the star of  the show!

Male bullfinch

Male bullfinch

IMG_2077Bullfinches are usually found in pairs as they mate for life so hopefully there is a female and a few mini finches around somewhere!

We also caught a few whitethroats and greenfinches which was nice as we don’t tend to get them at the nature reserve around the other side. Also a few recently fledged blackcaps, great tits and blue tits. The blue tits definately rival the long-tails on the cuteness scale!

Blue tit fledgling

Blue tit fledgling

Blue tit fledgling tail shot

Blue tit fledgling tail shot

Blackcap fledgling

Blackcap fledgling

Blackcap fledgling wing shot

Blackcap fledgling wing shot

The juvenile blackcaps (both male and female) can be tricky as they initially appear similar to adult female blackcaps. A closer look at the undertail coverts and you can see these feathers are brown and ‘fluffy’ as apposed to the light grey, sleeker feathers of the adults. Their underparts are generally more fluffy and brown and they have a duller cap compared to the chestnut of the adult females. The juvenile males may have a few wisps of black in their brown caps, otherwise it is difficult to sex them at this stage.

Juvenile blackcap undertail coverts

Juvenile blackcap undertail coverts

In between ringing there was also a bit of invertebrate action with numerous cinnabarbrown silver-line and light brown apple moths, a couple of small tortoise shell and holly blue butterflies, a raft spider and my personal favourite this swollen-thighed beetle – reminds me of those track cyclists with the giant thigh muscles!

Swollen - thighed beetle, Oedemera nobilis

Swollen – thighed beetle, Oedemera nobilis