brewood ringers

Results of a Ringing Expedition to the Parque Ambientale, Vilamoura, Portugal

30^th September-7^th October 2009

Colin McShane; Dave Clifton; Rob Skeates; Glynn Middleton; Stu Brown; Fergus Henderson; Sean Micklewright; Simon Davies; James Morris

Introduction:

After two very successful trips in 2007 and 2008, it was decided to visit the site a little earlier than previously, especially in order to connect with some of the local breeding migratory species such as Subalpine warbler ( Sylvia cantilans), whilst still hoping to catch significant numbers of northern migrants such as Bluethroat ( Luscinia svecica). On both counts this was a successful trip. Less successful unfortunately were our attempts at catching some of the rails and crakes in the marsh areas by means of small cage traps. We still feel this is worth pursuing given the fleeting glimpses we had of small rails from time to time. It must be worth trying to find out if the site is hosting either Little and/or Baillon’s crake, so we need to perfect our technique prior to any future visit. Great support during the planning and implementation was again supplied by our contacts and friends in Portugal, Nuno Grade, Vitor Encarnacao, Michael Armelin and Ana Luisa Quaresma.

Methodology:  

Catching used on average 13 Japanese/Polish mist nets, set at fixed positions almost entirely set in the same positions as the previous year to provide good comparison. However, because we had a much bigger team of ringers than in previous years, we also decided to set an additional series of around 10 nets deeper in the semi dry area of the marsh, where in previous years we had only exploited for roost netting. Nevertheless, as in the past, given the size of the reserve, the fact that most nets were set within about 400m of the base camp near the observation hide, a very small proportion of the parque was covered. This is again important when trying to estimate the total number of birds which use the area for feeding, resting and roosting at this time of year.

Nets were erected at around 07.00 hrs each day, with sunrise around 07.30 hrs. They were manned continuously and checked every 20 minutes or so. Weather conditions during the week were good, and ringing carried on continuously with nets being furled at around 19.00 hrs apart from those used for roost catching which were furled around 20.00 hrs.  On the final day, nets were taken down from about 10.00 hrs to enable the team to pack ready for the flight home. Audio lures were used occasionally, primarily for Bluethroat ( Luscinia svecica) at first light, Corn Bunting ( Emberiza calandra) and Barn Swallow (Hirundo rustica) at roost, and various other species periodically—with varying degrees of success.

All birds were ringed using CEMPA rings, and all were processed to record, age, sex, weight and maximum chord wing length. Migrant species were also estimated for fat score using the 5 point Euring scale.

Results:

The overall number of newly ringed birds is shown in Table 1. This also shows the number of each species ringed each day. This has enabled some further analysis ( see later)

Table 1 Daily species totals for 2009; and overall comparisons with 07 and 08

As well as some ‘same-site’ recoveries of birds ringed during the week, there were 5 notable recoveries/controls, about which original ringing data have not yet been received:-

1) 2 Reed warblers and 1 Bluethroat originally ringed in Holland

2) Bluethroat originally ringed in Belgium

3) Chiffchaff originally ringed in Jersey ( Channel Islands)

Analysis:

As the data are building each year, so our analyses become more significant—however, we must always appreciate that the ringing is carried out during one week only and cannot hope to give such significant data as a constant effort throughout a season could produce. Nevertheless we have tried to point to trends or issues which seem to be supported by the data.

What is again evident however, is that the Parque Ambientale is an important site for both resident and migratory birds. Each visit has produced a few birds originally ringed further north in Europe, thereby showing how important the area is as a staging post for migrants either on their way further south or in settling down for the winter months. Comments made in the previous report relating to the presence of and difficulties in estimating numbers of some groups such as rails, crakes, sparrows, starlings and buntings are still relevant. Put simply, the regime of catching used currently underestimates the population of all of these groups.

Overall totals:

The total number of birds ringed this year was lower than both previous years. When taken in conjunction with the fact that more nets were set than in previous years, it is clear that there were not the same numbers of birds available as in the recent past. At least two reasons were apparent. First, the concrete lined canal along which water from the treatment works flows into the main river, had been completely cleared of the encroaching vegetation. This had a significant effect on the birds we caught in the nets set in these areas because there was simply not the areas for feeding in such vegetation as in previous years.

Second, the number of new birds caught fell dramatically towards the end of our stay. This was due to weather conditions in northern Portugal, Spain and southern France during this period. Southbound migrants were able to leave Vilamoura under clear skies and light winds-but were not replaced by incoming birds since these were being held up further north by stormy conditions.

However, the number of species caught was by far the highest since we started. Again, we feel there were at least two reasons. First, the timing of our visit ( slightly earlier) meant that there were some late local breeders still in the area eg Melodious warbler (Hippolais polyglotta). Second, nets in different habitat caught different species; Wryneck (Jynx torquila), Nightingale ( Luscinia megaryhncos), Linnet ( Carduelis cannabina). In addition, good fortune is always important (eg Tree pipit ( Anthus trivialis)caught in the idle of a reed-bed)!

Resident species:

The use of extra nets this year has made some comparisons difficult. For example it appears as if Cetti’s warblers ( Cettia cetti) have increased, whereas this is almost certainly a reflection of more nets in suitable habitat. The apparent increase in Waxbills ( Astril estrilda) is similarly affected by amount of netting—but also by the increase in roost netting, where these birds are often caught as they return from their feeding visits to outlying areas. We were asked not to ring Weaver sp., hence the zero total, although re-traps were processed and recorded

However, the decline in certain species is made even more significant given that more nets were used. Both Kingfisher ( Alcedo athis) and Zitting cisticola ( Cisticola juncidis) show continuing steady declines over the last three years. We can offer no reasonable rationale for this. The disappointing number of Corn buntings ( Emberiza calandra) caught, despite our increased roost effort, was probably because birds were seen roosting in a new area of the reedbed which we found inaccessible, and the tape lures used were unable to attract them in large numbers into the netted area. House sparrows ( Passer domesticus) appear to be increasing.

As mentioned in previous reports, any additional data on breeding would add to the analysis, as will the re-trap data provided by our visits.

Migrants:

The addition of Barn Swallow ( Hirundo rustica) and Sand Martin ( Riparia riparia) is considered simply a feature of their chance occurrence at a roost and good attraction to the tape-lures, since only small numbers of both species had been seen feeding then moving off the reserve during most days.

The numbers of Robin ( Erithacus rubecula), Blackbird ( Turdus merula), and Blackcap ( Sylvia atricapilla), are consistent with our earlier visit, and with incoming migrants slowing as the week went on. These species typically move into the area during this time of year, many individuals remaining over winter before moving north in spring. Bluethroat ( Luscinia svecica) shows similar behaviour and it is thought the increase in the numbers of these caught could be a reflection of the fact that they tend to move into the area earlier than the above species, and perhaps a rather larger proportion of this species continues further south into northern Africa for the winter?

The higher numbers of Whitethroat ( Sylvia communis) and Willow Warbler ( Phylloscopus trochilus) is probably a function of our earlier visit in that these are typically early autumn migrants which move through the site quite quickly. The increased number of Subalpine Warblers ( Sylvia cantilans) may be for a similar reason, although prior to our visit, Michael Armelin had suggested that this species was commoner than usual, so perhaps they have had a good breeding season.

During our conversation, Michael also suggested that Reed Warblers (Acrocephalus scirpaceous) were less common than normal. Our data supports this to some extent, in that we would have expected somewhat higher numbers than we got given our earlier visit, and the extra netting. The lack of incoming birds however, did depress the numbers we could have expected. The earlier visit acted in the opposite way for Chiffchaff ( Phylloscopus collybita) as did the slow-down in migration at just the time when we would have expected increasing numbers of this species to be arriving.

Recommendations:

The continued success of this venture demonstrates yet again that the scope for catching and ringing birds as one aspect of monitoring on the reserve is very good. Furthermore, the addition of year-on-year data, while not yet providing conclusive answers, is beginning to elucidate some of the migration strategies and possible breeding successes of birds that use the parque. It is therefore important that we try to continue the visits, and if possible increase the ringing effort.

There remains the potential to improve the habitat by virtue of a shallow ‘scrape’ with mud and open water ( perhaps controlled by a simple sluice) to the north-west of the main observation hide. If this could be achieved it would provide a great attraction to wading birds which are poorly represented in the parque at present. It may be that this could become a reality depending upon forthcoming negotiations.

There is now an increasing amount of re-trap and control data which we hope will be of use in a variety of ways. If there is anything we can do to assist in the analysis and interpretation of this data, we would be only too willing to help.

Finally, we would like to thank the management of the Parque Ambientale for allowing us access to the site during our stay, and to Vitor Encarnacao and Michael Armelin for providing us with the necessary permits, rings and some extra poles. We are immensely grateful also for the support during the planning stages and when on site from Nuno Grade, and Ana Luisa Quaresma, who again made us very welcome and helped in a great many ways to make our visit successful.