Mytilus edulis

In this part of the world, Blue Mussels Mytilus edulis usually don’t get harvested on hot summer days. The only people after them around that time are hardworking scientist, often operating in extreme heat. This was by far the coolest place to collect them, from the Ria de Aveiro.

Old Cormorant

Colour-ringed Great Cormorant Phalacrocorax carbo, roosting along the Ria de Aveiro, near Bunheiro (Portugal) on February 24, 2015. Ringed as nestling at Lac de Grand-Lieu (Loire Atlantique, France) on June 16, 1998, by Loïc Marion. This is the birds’ first sighting.

Great work on little brown jobs in Salreu, Portugal (September 8 & 9, 2014)

More information and the results of two enjoyable mornings of ringing in the marshes of Salreu with Julio M. Neto can be found here:

September 8: https://sites.google.com/site/juliomneto/blog/alatestart
September 9: https://sites.google.com/site/juliomneto/blog/onemorebritishrecovery





European stonechat Saxicola rubicola







Cetti's warbler Cettia cetti




Common waxbill Estrilda astrild







Bluethroat Luscinia svecica
 



Tree pipit Anthus trivialis







Sedge warbler Acrocephalus schoenobaenus







Weighing a ..?

No die-off yet.., just many dead gulls

In response to my announcement of a ‘gull die-off’, Professor Antonio Luis (University of Aveiro) informed me that this part of the Ria de Aveiro is part of a very wide basin, which has several industrial areas, agriculture, cattle, etc. The road network is relatively dense too. It's also known that the lagoon itself is very polluted at some points, from very local sources. On the other hand these were the first rains in a long time, there were lots of wildfires during summer and now there's nothing to hold both the rain water and the burned ground (as well as what's in it). As a consequence everything is easily washed away, down into the lagoon and flood plains. In summer, when the water gets warmer, it's also common to have toxin blooms (shellfish capture is not allowed during these periods) and these maybe nasty toxins sometimes... The number of possible causes may be pretty big.

In order to investigate the true scale of this thing, and whether we’re experiencing a true die-off or not (in which the population undergoes a sharp decline), during yesterdays afternoon I walked 2 km on and along the shoreline and sand dams of the Ria de Aveiro, near the UA. This track included the 300 m transect I mentioned earlier.

On this track I found the remains of a total of 25 Lesser Black-backed Gulls, 5 Black-headed Gulls and one Common Redshank. Most of the LBBG carcasses were old (17 >multiple weeks/months/a year), one was fresh (the affected live adult that I found on October 6) and 7 probably died within the past three weeks. Most (at least 20) of these were adult plumage birds. Of the BHG carcasses (all adults), one was older than months and 4 had died during the past few weeks. I suspect this has been a slight undercount as not all of the tide line was accessible (about 20% remained unchecked). I found one possibly affected live bird, a solitary adult LBBG in the active salinas, which I could not approach. None of the carcasses I checked was marked.

 

 Older, subadult LBBG carcass

At the salinas and in the Ria there were about 450 LBBG and 170 BHG roosting. Later, at dusk, came roughly 900 LBBG and some BHG over my head from the direction of the local landfill, of which a varying number roosts in this part of the Ria.

This would indicate that the scale of whatever is/was going on seems indeed not to be alarmingly large, at least not in this (relatively isolated) part of the Ria, and no immediate action needs to be taken. Just to be sure, next time I’ll try to investigate a slightly more northern area to see how the situation is there (closer to the ocean's entrance, where several dying gulls had been reported earlier). Let’s hope that whatever this is or was has come to a halt by now, as these dying gulls always are a nasty sight. Considering the scale of this event I am very sure that there will be at least some marked individuals among the recently deceased birds. I will try to keep an eye out for those and recommend local readers of this blog to do the same.

Gull die-off in the Ria de Aveiro

Once a week the dog gets a walk along the a few hundred meter long sand dam on the Ria de Aveiro, at the height of the University of Aveiro. On this walk I identify and count fresh carcasses of birds (and once a feral cat). About three weeks ago I started to notice a rapid increase of dead Lesser Black-backed Gulls and Black-headed Gulls. I usually find (depending on the time of the year and the number of gulls present in the area) about 0-1 gull carcass on each trip. Within the past three weeks I found there the carcasses of 10 LBBG (9 adult and 1 immature) and 4 adult BHG. About two weeks ago I spoke with 'Ines', a UA student who also walks with Juli along the Ria at the height of the university. At that time she told me Juli ran onto the mudflats while chasing a dark gull that could not fly. On October 3 I got informed by an inhabitant of Sao Jacinto that he had noticed an unusual high number of deceased and dying LBBG out on the most southern dam of the peninsula, about 7 kilometers from the earlier location. He told me he found 21 gulls of which a few were still alive. These live birds were unable to walk and were turning their heads backwards in an odd way. Today Flor and I walked our transect again and ran into this adult LBBG showing symptoms of poisoning. About 40 meters from us was another adult LBBG present on the water surface which appeared to be trying to fly, though it did not manage. There were no new carcasses present on the transect, but the recent high tide could have swept away most of the dead matter. I regularly count the number of live LBBG and BHG present at this part of the Ria, which, during today’s upcoming tide, was surprisingly low, compared to earlier high tide visits. I have informed Biology student 'João' from the University of Aveiro about this situation in the hopes that the situation can be investigated. Luis would inform his supervisors about this, what seems to be fair to call, gull die-off in the Ria de Aveiro.

Osprey (Pandion haliaetus) taking a dip

Today a short visit was made to the salinas near the University of Aveiro, in the hopes of finding a good number of gulls and rings. The tide was coming up, which is usually the best moment to find many gulls there. As the mudflats become inaccessible to the gulls, they’re forced into the salinas, closer to the observer. At arrival, however, no gulls were present, but small numbers of Lesser Black-backed Gulls (250) and Black-headed gulls (300) were present elsewhere in the Ria de Aveiro, well out of scope range. I suspect that these birds had either been flushed by weed-whackers, or had been scared off from the site more permanently due to the current salt harvest. Only one ring was observed but not read; a metal ring around the left tarsus of an Osprey that was first taking a bath and then dried its wings for about half an hour. Who would have thought that a bird that plunges in the water so regularly would take time for a bath? It turned out to be not the same individual as was observed wintering at this location during the previous winter (which had a large metal clip ring around its right tarsus; see the other two posts with the ‘Osprey label’).

Lack of gull rings leads to the reading of a Limosa spec.

Today a poorly scheduled, but sunny, visit was made to the fishing harbor of Gafanha da Nazaré, near Aveiro. Due to a low tide and little fishing activity not many gulls were present, only about 750 or so. A few thousand were roosting on the sand banks of the Ria, but these were out of the range of my scope. Only seven rings were read, which were applied in Denmark (2), The Netherlands (2), Guernsey (1), Southwest England (1) and France (1).

LBBG YELLOW E222/E from Norman van Swelm (The Nethelands)

BLACK 1AK2 was the only LBBG from Guernsey that I could find; the others will most likely be hanging around on the landfill.

   

Immature LBBG GREEN Y.BFX, also from The Netherlands.

 Peter Rock's BLACK J+J, all the way from around Bristol and now behind bars in Portugal.

After this rather unsatisfying visit I thought it would be a good idea to inspect the situation at the University of Aveiro. In one of the fresh water ponds I ran into a marked Mallard male (89/S/89), which was the only marked duck among the 40 Mallards that I found. At the nearby mudflats of the Ria de Aveiro I found barely any gulls within my scope’s range, but instead I found about 2000 Limosa specs. After scoping out about 15 of these I ran into this ringed individual. No idea what subspecies, where it’s from or who ringed it, but I’ll true to figure this out. After taking a second photo of this bird, thankfully all of them took off so I did not have to deal with more of those tiny plastic ring codes.