Sunday, 18 August 2013

Titchfield Haven - Bird Ringing Second Update August 2013

Bird ringing at the Haven was restricted to the Saturday only this weekend since it was forecast to be very breezy on Sunday. At 5 am it was flat calm, not a breath of wind, and before long it was evident that there had been a good movement of birds. Grasshopper warblers were the first species caught, but as seems to be the pattern this year they were not present in particularly high numbers, only seven new birds were ringed. By contrast sedge warblers have been abundant this year, and that pattern continued, with 106 new birds ringed. Reed warblers also were in good numbers with 54 new birds ringed, but the surprises came in the form of garden warblers and common redstarts. 

First Winter male Common Redstart

I have previously written about common redstarts since it is a species that we don't catch very often, in fact one or two a year is a good result. On Saturday two first year male birds were trapped and ringed within the first hour, our first two of the year. 

First Winter male Common Redstart

Male birds are very obvious since they exhibit a dark throat, evidence of a white eyebrow and a grey mantle, as can be seen in the image above. The bigger surprise was the numbers of garden warblers. This is a species that we will typically catch around 100 birds a year, and on a good day will catch 10 new birds. This weekend we caught 24 new birds in one morning, which was astonishing. The total included two adult birds but the rest were juveniles. 

By the end of the session we had ringed 217 new birds, so not as many as the previous weekend but a good haul all the same. The total included 106 sedge warblers, 54 reed warblers, 24 garden warblers, nine willow warblers, seven grasshopper warblers and six common whitethroats.

Looking at the numbers I was intrigued to see how this year compared to the last few years, since 2011 had been exceptional for many species whereas 2012 had been a dreadful. Below is a graph and table giving the ringing totals at the haven between the start of each season between 2010 and 2013 to 23rd August 2010 and 17th August 2011 - 2013 . To ensure that the analysis was comparable I compared the same dates where I could, although it was not possible for 2010. I hope you will agree that it makes interesting reading.

Comparison of Ringing Totals between 2010 and 2013 at Titchfield Haven

The numbers of sedge warblers ringed this year are on a par with the record year of 2011, and reed warbler numbers are in fact higher. Presumably this indicates that both these species have had good breeding seasons. Willow warbler numbers are higher than 2012, but the overall trend for the last four years is still down and grasshopper warbler numbers are on a par with 2010, which was the last average year. Garden warbler numbers are slightly up, albeit boosted by the record day on Saturday, and blackcap numbers mirror those of 2010. Common whitethroat numbers have not recovered from the 2012 low, but Cetti's warblers seem to have had an excellent breeding season.

Table of Ringing Totals between 2010 and 2013

So what does all this mean? Well it is difficult to really say at this point in the season, since it may be just that birds are still breeding due to the good weather. Last year we recorded a higher percentage of adult birds than normal at this time, indicating that birds had given up breeding and started to migrate south. This year the number of adult birds recorded for most species has been low, for example grasshopper warbler only two so far and only two out of 24 garden warblers on Saturday were adults. I will do this analysis again at the end of the season so it will be interesting to see how things pan out then.

Friday, 16 August 2013

On the Lookout for Grasshoppers at Noar Hill - 15th August 2013

I had the opportunity to get out of the office yesterday in order to carry out an Orthoptera (Grasshopper and Cricket) survey at The Hampshire and Isle of Wight Wildlife Trusts Noar Hill Reserve. The main purpose of the visit was to check on the status of rufous grasshopper, a species that is known to be present, but had not been searched for recently. It is a species that is restricted to southern England on south-facing slopes of unimproved calcareous grassland, Noar Hill provides the ideal location for the species and has known to be present for many years.

Classic piece of chalk grassland at Noar Hill

The reserve was once the site of medieval chalk workings, but is now owned by the Wildlife Trust. In the spring and early summer it is carpeted with chalk downland flowers, including many species of orchid.

Harebell Campanula rotundifolia

I was hoping for a warm, still and sunny day, since these are the best conditions for Orthoptera surveys. Unfortunately it was quite windy and cloudy, so sunny periods were interspersed will long periods of shade, the temperature dropped considerably during these periods. Over 35 species of butterfly have been recorded at the site, and it wasn't long before we were seeing some of them. Chalkhill Blue was the first species recorded, keeping low in the vegetation but occasionally basking during a sunny interval. This species appears to have had a great year, as on the Wildlife Trusts Arreton Down reserve on the Isle of Wight, a few thousand individuals have been on the wing in recent days. A spectacular sight if you can get there to witness it!

Male Chalkhill Blue Lysandra coridon

Several common blue butterflies were also on the wing, although not as many as there were chalkhills, and the supporting cast included small heath, meadow brown, large and green-veined white and gatekeeper.

Male Common Blue Polyommatus icarus

Hemp-agrimony provided a rich source of nectar for more species, especially peacock, small tortoiseshell and a handful of clouded yellows that were scattered around the site. The latter proved incredibly difficult to photograph as they were easily disturbed, and were being blown around in the gusty conditions.
Peacock Inachis io

Underwing of Peacock Inachis io

Along the woodland edges silver-washed fritillary's, brimstone's and Comma's were also taking advantage of the rich nectar source provided by the hemp-agrimony.

Silver-washed Fritillary Argynnis paphia

Silver-washed Fritillary

Grasshoppers and crickets were proving difficult to locate since they were not really singing in the unfavourable conditions. Dark bush cricket was the first to be heard, and soon meadow, common green and field grasshopper had also been added. Roesel's bush cricket is one of those species which has expanded rapidly since being first recorded in the extreme south-east of the country. A handful of this species were recorded in the areas of taller vegetation, along with a few long-winged coneheads.

Sheltered sunny glade which proved to be a great location for
Rufous Grasshoppers

Eventually, after several hours of searching, a male rufous grasshopper was recorded in a sheltered glade in the east of the site. This species is one of the easier grasshopper species to identify due to the presence of a range of features, some of which are unique and are present on males, females and nymphs.

Male Rufous Grasshopper Gomphocerippus rufus

The grasshopper is generally brown in colour and usually has a reddish abdomen. The male has large club shaped antennae, similar to a butterfly, that are tipped white, these are diagnostic. They do also occur on females and nymphs but are not as pronounced, as can be seen in the pictures below.

Female Rufous Grasshopper

They also have pale palps, which are located by the mouth parts, and the call is like a clockwork toy unwinding. It is a late maturing species and with adults not usually found until late July, but they can survive until late November and even early December.

Rufous Grasshopper - Final instar nymph

Another species restricted to south-facing calcareous slopes in the south of England is stripe-winged grasshopper. It is quite a widespread species and can be quite common in some places. It has a very distinctive call that lasts about 10 to 20 seconds, it is very high pitched, starts with a hiss and then continues with a buzzing, metallic, pulsating sound.

Stripe-winged Grasshopper Stenobothrus lineatus

One distinctive feature is the enlarged central cells of the forewing, you may need a hand lens to see it, but it does tend to give the grasshopper the appearance of having a broad wing.

Enlarged central cells on wing of Stripe-winged Grasshopper

By the end of the visit eight species of Orthoptera had been recorded, including the target species and 13 species of butterfly. Not bad for a blustery afternoon in Hampshire.

Saturday, 10 August 2013

Titchfield Haven - Bird Ringing Update August 2013

The bird ringing season is already well under way at the Haven, and after a slow start the autumn migration is now in full swing. Despite the slow start the daily totals were bolstered by good numbers of breeding residents with the Cetti's warblers being the most numerous species. To date 33 different birds have been captured, with 25 of those juveniles and three new adults, the rest were retrapped adults. Evidently this species has had a good breeding season.

The grasshopper warbler migration started about 10 days later than last year and has so far not reached the dizzy heights of previous years. In fact we have only been averaging 12 birds per day and this year have only ringed 147 birds; all of those have been juveniles. Sedge warbler numbers have been very good and today (10th August 2013) a catch of 272 birds (including 6 controls) was made up of 187 (including 3 controls) birds making the total for the year 647. This week an extraordinarily dark juvenile sedge warbler was captured.

Dark Sedge Warbler Acrocephalus schoenobaenus (B.S Duffin)

As can be seen from the pictures the bird was generally dark rusty brown in colour on both the upper and underparts, a truly striking individual.

Underparts of Dark Sedge Warbler

Surprisingly this is not the first time I have seen a bird with this colouration. In 2010 a similarly coloured reed warbler was trapped at the Haven during the autumn migration. This bird was different in that it seemed to have a brown sticky mess on its forehead, which suggested that the bird may have fallen into something, this did not appear to be the case with the sedge.

Dark Reed Warbler A. scirpaceus from 2010

The pattern of migration this year is again similar to previous years with sedge, reed and grasshopper warblers being the most numerous. Willow warbler numbers are now starting to build and today we ringed 17 new birds bringing the total to date to 50. All of the willows were again juveniles including a very pale washed out individual. According to Svennson northern populations are more greyish-white and generally lack any yellow tones.

Juvenile Willow Warbler Phylloscopus trochilus of the northern/acredula type

This bird was was exactly that, a pale greyish-white bird with no yellow tones. When compared with a typical willow warbler it was possible to see just how striking the bird was.

Willow Warblers - both these birds had a wing length of 61.5 mm and therefore
we thought that they were ideal for comparison. The pale left bird weighed 7.4 grams
whereas the normal right bird weighed 8.5

And if an unusual sedge and a northern willow wasn't enough, we were also treated to a very smart wood warbler. Every year we try for this species and have only ever caught a handful. Today's bird was the first for four years and added to what was an excellent days bird ringing.

Wood Warbler Phylloscopus sibilatrix the first ringed at the haven for about four years

Our tally today included six controls, three each of sedge and reed warbler. That brings our total of outstanding controls for the autumn to 18 including one French and one Spanish, and we are not even halfway through the season yet. Our total for new birds ringed stands at 1309 birds of 24 species, 108 birds have been retrapped.

Monday, 5 August 2013

Gone Batting!

In preparation for some bat survey training that I will be giving later this week, I popped down to Hook Barn this evening to collect some droppings. I have to admit that I ventured there with some trepidation because the last time I went in, I found six dead brown long-eared bats. The circumstances of their deaths is not really known, but I won't dwell on that and hope that it won't happen again.

Usually at this time of year I would expect to see a huddle of brown long-eared bats in the apex of the roof, but this time there were none. It was not a complete disaster though, because there were plenty of fresh long-eared type droppings thereby confirming that there has been some activity.

Looking around the barn it wasn't long before a found a pipistrelle bat (probably common) in the apex of the roof, and this cracking serotine!

Serotine Eptesicus serotinus
For the last couple of years up to two, but usually one serotine has been present in the barn. Given that it is usually just the one bat I suspect it is a male, which would mean that there may be a maternity colony somewhere nearby. This is one of the bigger bat species that inhabit the British Isles and they come in two distinct colour morphs. This bat was dark brown above but still fairly pale underneath; I have seen them much darker previously.

Brown Long-eared Plecotus auritus

It was also nice to find a brown long-eared in the apex of the roof too. This individual was very torpid and you can see how it has folded its ears back beneath its forearm; a classic pose for this species when roosting. It was worrying not to see more that one long-eared in the barn, although it is possible they are clustered beneath ridge tiles, or elsewhere in the barn. Over the next few weeks I will do a dusk emergence survey to see just how many bats are still present.

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