Scouse Ringer no Verão: Post-breeding Moult in Adult Grasshopper Warbler

Following on from a post I made a few weeks ago about a Reed Warbler that had undergone a partial flight feather moult, I thought that a Grasshopper Warbler that we caught at Madriz on Thursday would be of interest.

The Grasshopper Warbler (Locustella naevia) is an example of a species in which the adults complete a partial post-breeding moult (unlike Reed Warblers that will replace body feathers but not flight feathers - with a few exceptions). The birds complete the moult on the breeding grounds once they have finished breeding which is often the determining factor in the extent of the moult. Food availability and environmental conditions also influence the amount of energy that a bird can dedicate to moulting.

This Grasshopper Warbler has moulted its tertials, the innermost primary and all but one of its greater coverts.

Grasshopper Warbler (Locustella naevia)

As all of the Grasshopper Warblers that we catch here in Portugal are migratory, the birds are often carrying large fat deposits that they need to provide energy in order to make the long crossing across the Sahara. Last week we captured a bird with a mass of 19.7g which is impressive given that the lean mass of a Grasshopper Warbler is between 11 and 13g.

Scouse Ringer no Verão: Maís Limícolas

I've been pretty busy here in Portugal since I last posted, so here's just a quick one featuring some pictures from the second wader-netting session at Estuário Mondego. It was a relatively successful session with the diversity of species more varied from the previous catch but still in low numbers. The tide was higher than the original session and due to the salt pan being abandoned, the tide was able to flood the pans at its highest point meaning that the catch tailed-off earlier than expected.

 Dusk on the salt pans

 Rita ringing a Dunlin

The ringing team - Luís, André, Miguel, Pedro, Rita and Tineke

Little-ringed Plover (Charadrius dubius)

Dunlin (Calidris alpina) - top, Little Stint (Calidris minuta) - bottom

The totals were:

Little Stint -   1

Little-ringed Plover - 1

Dunlin -    24

Ringed Plover - 9

TOTAL:   35

Scouse Ringer no Verão: Parque Biológico de Gaia

I've been pretty busy so far this month which is why I forgot to get around to posting some pictures of a visit that I made to Parque Biológico de Gaia at the end of July. Following our trip in the Minho region, that you can read about here, here and here, we stopped off at PBG to help out with the ringing of a number of birds that had been rehabilitated following injury or entrapment before release.

Parque Biológico de Gaia is found in the Vila Nova de Gaia area on the opposite side of the mouth of the Douro to the city of Porto. The municipality has been very proactive over the years in protecting local areas for wildlife as well as taking a progressive approach to environmental education. My colleagues in GVC run fortnightly ringing sessions at PBG and these sessions are open to the public to come and see what bird ringing is all about.

PBG also has a wildlife recuperation centre and often receives birds from the police as well as members of the public. In fact, the majority of the birds that were ringed, were finches that had been confiscated from illegal bird traders. Most of the birds were Serins, but there were also a good quantity of Linnet, Chaffinch and Greenfinch. Those birds healthy enough to be released, after being checked by the vet, were ringed and released.

In addition to the finches, there was this quite beautiful Great-spotted Cuckoo. This bird had been received as a young bird and had been in the centre for a while, given a clean bill of health, the bird was ringed and released.

                                                                    Great-spotted Cuckoo (Clamator glandarius)

Great-spotted Cuckoo

Another project that GVC are working on at the moment, regards the colonisation of the city of Porto by Yellow-legged Gulls (Larus michahellis). As part of the project, birds will be ringed with both a metallic ring and a colour ring to allow birds to be identified from distance. In the first phases, most birds being colour-ringed are juveniles that fell from nests in the city, were brought to the centre, rehabilitated and then released. The next phase will involve ringing juveniles on the colonies. 

A number of Yellow-legged Gulls that were ready for release were colour-ringed, including this, rather handsome, adult that was recovering from a broken wing.

Yellow-legged Gull (Larus michahellis)

Scouse Ringer no Verão: Locustella

In Portugal, it is possible to catch two different species of Locustella Warbler at different times of the year, Savi's Warbler (Locustella luscinioides) and Grasshopper Warbler (Locustella naevia). Only the Savi's Warbler breeds in Portugal, whilst the nearest breeding territories of the Grasshopper Warbler are in northern Spain.

At this time of year, as Grasshopper Warblers are undertaking their migration to the wintering grounds in Africa and Savi's Warblers are either completing their post-breeding moult (adults) or building up fat reserves for the journey south, it is possible to catch both species. The ringing site at Estuário Mondego is not ideal habitat for catching Savi's Warblers as the catch area is almost exclusively reed bed and the Savi's favours juncus grassland, however, so far we have caught and ringed six. The first Grasshopper Warbler was caught on 8th August and these have started to move through is small, but steady numbers in subsequent sessions with a total of ten ringed to date.

Juvenile Savi's Warbler (Locustella luscinioides) - this bird was aged as a juvenile due to the yellow colour inside the bill. An adult bird would display a pink/grey colouration.

Juvenile Grasshopper Warbler (Locustella naevia) - this bird was aged as a juvenile due to the condition of the plumage. Unlike Savi's Warblers, adult Grasshopper Warblers do not complete a full post-breeding moult before migrating, this means that adults would demonstrate a more worn plumage to juveniles.

For those unfamiliar with either the Savi's or Grasshopper Warblers, they are similar in behaviour with both birds difficult to observe in the field as they skulk in long grass and are often heard rather than seen. In terms of their plumage, they are suprisingly silky, despite their behavioural habits that would suggest their plumage would be in a more damaged condition.

One of the defining charateristics of the Locustella warblers it that their longest undertail coverts are longer than the shortest tail feather, as you can see below. This however, is a characteristic that is usually only observed whilst the bird is in the hand.

Untertail of Grasshopper Warbler (Locustella naevia)

  Undertail of a Savi's Warbler (Locustella luscinioides)

 
During the rest of August and into September, the number of these species caught at migration monitoring sites on the Iberian peninsula will start to increase as birds build up their fat reserves and begin to make the flight over the Sahara to their wintering grounds.

Scouse Ringer no Verão: Limícolas

As part of this summers migration monitoring in the Mondego Valley, a gang of us met up on Sunday night to take advantage of the near-new moon and subsequent high tides to try and catch waders on an abandoned salt pan in the Mondego Estuary. At low tides, flocks of waders feed on invertebrates found in the mud flats in the estuary of the river, but as the tide rises, and the mud is submerged, the flocks move onto the salt pans in search of food.

We set up three lines of single panels nets in a 'H' formation just after dark. With the high tide at midnight, this was when we expected to catch the majority of the birds and right on cue, the birds arrived and we got down to processing.

The majority of the birds were caught in the first two net rounds and consisted of Dunlin and Ringed Plover. Upon extraction, one of the Dunlin was ringed and, continuing our recent run of foreign-ringed captures, it was revealed that the ring read: ARNHEM VT HOLLAND.

 

ARNHEM Dunlin (Calidris alpina)

 

                                                                          Ringed Plover (Charadrius hiaticula)

Dunlin (Calidris alpina)

The subsequent net rounds yielded only a couple of birds each so by 4am, the nets were packed away and Miguel and Luis headed off to open the nets at Taipal and I headed down the road to pick up Moxey for our morning session.

Dunlin -   21  (1)
Ringed Plover -   7

TOTAL:    28   (1)

Moult in Adult Reed Warbler

The Reed Warbler (Acrocephalus scirpaceus) is a bird that I am particularly familiar with, having ringed thousands over the years during migration projects, especially here in Portugal. A lot of European migration monitoring stations and bird observatories deal with large numbers of Reed Warblers on migration and subsequent work completed in Africa means that we (relatively speaking) know quite a lot about them.

Moult can be one of the more complex phenomena that trainee ringers need to study. An understanding of the behaviour and moult strategies of individual species can be critical in determining the age of the bird. In some cases, as with raptors, gulls and owls, this can be done into fourth or fifth calendar years, in some cases more. With most passerines, we are limited to two or maybe three options depending on the time of year. Those options are:

• The bird hatched this calendar year - considered a juvenile. Age code 3.
• The bird hatched in the previous year but encountered before the bird has moulted into its 'adult' plumage. Age code 5 (After Jan 1).
• The bird hatched in the previous calendar year or earlier - this bird is considered 'adult'. Age code 4 or 6 (after Jan 1). In fact, birds encountered in this phase could be three, four, five or more calendar years old, but in terms of plumage, it isn't possible to determine this.

On 3rd August, during a ringing session at Madriz, an adult Reed Warbler was captured that displayed a curious moult. At this time of year, adults are easy to distinguish from juveniles. Juvenile have a very 'fresh' plumage, the feathers are all new, in good condition and the colours displayed are rich. Adults, on the other hand, have a much more 'worn' plumage, the feathers are degraded, the tertials are pointed and the plumage appears washed out.

The bird in question, had actually almost completed a full moult of primaries and secondaries (the main flight feathers). As you can see from the image below, the bird retained the two inner primaries and the three innermost secondaries. This is unusual because the adults only complete a full moult when they return to the wintering grounds in Africa. Why has the bird done this? We can never be certain, this bird may have intended to breed but for some reason failed in its attempts and completed the moult shown - moult is energy expensive and not compatible with raising young. Birds when captured during their moult phase are often heavier than they would be normally, due to the physical process of growing many new feathers.

Moult in an adult Reed Warbler (Acrocephalus scirpaceus). NOTE: Three retained inner secondaries and two retained inner primaries.

I wish I could write an article about the moult of Savi's Warblers (one species in which the adults do moult before returning to Africa), but I wouldn't do it justice - their moult strategies are eratic to say the least! Therefore I point you in the direction of an excellent paper by Julio Neto & Andrew Gosler entitled 'Post-juvenile and post-breeding moult of Savi’s Warblers Locustella luscinioides in Portugal'. This article can be found in Ibis (2006) 148, 39-49. Enjoy!

Scouse Ringer no Verão: Quality Control

This August, me and Moxey are ringing as part of the PADA group of ringers in the Mondego Valley area of Portugal. As well as ringing at long-term monitoring sites at Madriz and Taipal, we are also taking the opportunity to make a concerted effort to assess the importance of a recently formed reed bed in the Mondego estuary opposite Figueira da Foz. This involved completing, on average, three ringing sessions a week at the site and we've spent the other days at either Taipal, Madriz and also at Salreu further north, near Averio.

So far, me and Moxey have completed four ringing sessions at Figueria da Foz, ringing a total of 167 birds. Whilst the majority of birds have been standard reed bed fare (for this region), we have had a few points of interest:

• Three Great Reed Warblers ringed (two juveniles)
• Fourteen Sedge Warblers ringed (peak of seven on 4th Aug)
• Two Whitethroats ringed (first on 2nd Aug)
• First Melodious (4) and Grasshopper Warblers (1) ringed on 8th Aug.

The most interesting day from our point of view, was 5th August. In terms of the number of birds ringed, everything was as expected however, only three birds were caught that had previously been ringed. This isn't particularly unusual until......the first ring, on a Reed Warbler read: MUSEUM PARIS. Not bad! The next one, another Reed Warbler reading: INFORM MUS. JERSEY. Nice! I've never seen a ring from Jersey. Finally, a Willow Warbler reading: BRUSSELS! Awesome!

BRUSSELS

JERSEY

PARIS

That's three controls from three countries in one ringing session. These days don't come around that often and prompted a few cheeky text messages between group members.

Reed Warbler -   73
Great Reed Warbler -  3
Blackcap -   3
Whitethroat -   2
Wren -   2
Waxbill -  8
Willow Warbler -   14
Kingfisher -   4
Greenfinch -   6
Blackbird -   3
House Sparrow -   8
Sedge Warbler -   14
Nightingale -   3
Savi's Warbler -   4
Tree Sparrow -   4
Stonechat -   3
Fan-tailed Warbler -   1
Song Thrush -   1
Melodious Warbler -   4
Grasshopper Warbler -1
Blue Tit -   1
Cetti's Warbler -   1
Spotless Starling -   2
Song Thrush -   1

TOTAL: 165

Scouse Ringer no Verão: The Ciência Viva Sessions

Over the past two weeks we've run two Ciência Viva sessions in the Minho, at Veiga da S.Simao and at Paulo do Coura as well as participating in the Madriz session here in the Mondego. These 'open-house' sessions are for members of the public to come and witness science 'in the flesh'.

These sessions are also good opportunities to attract new trainees to ringing and a number of individuals expressed their interest in visiting future sessions.

Scouse Ringer no Verão: Paul do Coura

Following a three day stint at Veiga da S.Simão on the south side of the River Lima near Viana do Castelo, myself, Tó and assorted members of Grupo Viana do Castello headed to a site that we first visited at the same time last year, Paul do Coura. The Minho River seperates coastal Spain and Portugal in the north of the country, and it is at the estuary of one of its tributaries, the Coura River, that the reedbed is found. We base our ringing sessions in the more accessible, but lower quality' reedbed on the interior side of the river.

The fragmented reed bed - Spain in the background

Last year, our only session was extremely productive (read about it here) however this years three sessions, on consecutive days were less productive, despite more nets being used. As you can see from the species diversity between days, we experimented with nets in different areas in addition to the reed bed lines.

Of interest on the second day were the captures of a Sedge Warbler, an early migrant and a single Grasshopper Warbler, also pretty early. It is not especially unusual to catch small numbers of Sedge Warbler this early in the season, especially here in the north of the country, and a small amount had been caught a few days earlier by PADA at Pateira de Fermentelos during a Ciencia Viva session.

Grasshopper Warbler (Locustella naevia)

The first Savi's Warbler and Fan-tailed Warblers were caught on the final day, as was the recapture of the only Great Reed Warbler that was ringed last year. It would seem that Great Reed Warblers continue to struggle in terms of their population in Portugal as I have blogged about before.

Melodious Warbler (Hippolais polyglotta)

There was an unusually low number of juvenile Reed Warblers captured during the three day, suggesting a low reproductive output however this cannot be taken at face value. It is possible that the reed bed doesn't support a large number of breeding birds, possibly the juvenile birds favour the higher quality reed bed on the other side of the river with adults dispersing to the fragmented reed bed in which we ring. However, when discussing the matter with colleagues further south, some sites are reporting similar situations.

26th July

Reed Warbler -   32   (1)
Reed Bunting -   1
Melodious Warbler -   3
Linnet -   1
Waxbill -   9
Kingfisher -   1
Blackbird -   1

TOTAL:   48   (7)

27th July

Reed Warbler -   6   (7)
Robin -   6
Melodious Warbler -   2
Grasshopper Warbler -   1
Sedge Warbler -   1
Blackcap -   1
Blackbird -   2
Wren -   1
Waxbill -   10
Willow Warbler -   1

TOTAL:   31   (7)

28th July

Savi's Warbler -   1
Wren -   1
Willow Warbler -   1
Fan-tailed Warbler -   1
Waxbill -   3
Robin -   4
Melodious Warbler -   1
Reed Warbler -   14   (7)
Great Reed Warbler -   (1)
Blackcap -   2
Reed Bunting -   1
Blue Tit -   1

TOTAL:   30   (8)