Lisboa M037213: The remarkable (but not unexpected) occurrence of a Mallard on a landfill and something about a hunter’s contribution to science.

As reported in the earlier blog entry about my most recent visit to the Eirol landfill (which I visit on a regular basis for gull ring reading and good overall birding - http://www.timvannus.blogspot.pt/2013/02/eirol-landfill-february-5-2013.html), an inspection of the present gull carcasses at the site resulted in the recovery of two metal bird rings. One originated from a BTO/British Lesser Black-backed Gull (for which I did not receive its life history’s data yet) and the other from an unknown species, though probably not a gull.

Ring M037213, as it was found at the Eirol landfill on February 5, 2013

This particular metal ring (Lisboa M037213) was found on the bare sand of a yet unused part of the bottom of the landfill site. It was still attached to a (relatively short) tarsus and foot, of which the color of the flesh appeared to be orange. The ring itself was about the same size as used on the larger gull species. The whole set (leg and ring) had obviously been regurgitated by a gull at the spot, as it was lying among numerous other food remains at this gull roost.

The yet largely unused open dump site of the Eirol landfill, containing a large short term gull roost.

It did not take much effort to find out where and by whom this bird was ringed; the first birds with orange legs that came to my mind were ducks, so Portugal’s duck expert David Rodrigues (http://www.pt-ducks.com/) would be the right person to turn to. I help David on a regular basis with trapping, marking and monitoring ducks at the ponds of the Sao Jacinto reserve. As part of this ongoing project, captured duck are applied with a metal (Lisboa) ring and a unique nasal marker, allowing individual recognition of the released birds in the field, to study movements and migration, survival rates and fidelity rates to wintering grounds, as well as other aspects of duck bio-ecology.
In Portugal the annual survival of ducks is negatively influenced by widespread hunting activities. The idea is/was that when a hunter shoots a marked duck, he (or she??) will report the ring or saddle code, by which way insight is gained in the impacts of hunting on the duck populations. In the past some local hunting associations and their members have been informed about the existence of this project.

A marked and studied female Mallard, wearing the usual outfit of one nasal saddle (in this case S0/P/S0) and one unique metal ring.

David recently informed me that M037213 had been applied on an adult female Mallard Anas platyrhynchos that was captured at the duck pond of Sao Jacinto on August 3, 2011. This bird was also given a nasal saddle with the code M0/Y/M0. It weighed 885 grams, had a wing length of 156 mm and was moulting primaries in the duck pond of Sao Jacinto. After its release that same day it was never resighted, neither recaptured.

When M037213 got prepared for the kitchen, most of its leg got cut off, as the tibia appeared to have been cut through just above its connection with the tarsus (probably with a knife). M037213’s leg and ring were thrown in a bin and ended up on the landfill, where they got swallowed by a gull, regurgitated in the pit, and eventually found there and reported by me.
I don’t believe not reporting a ring is considered a crime; it is certainly lame from my perspective. From a hunter’s perspective it may be acceptable to dispose the evidence that another duck had been shot. But for the least metals should be recycled. They should not end up in compost, but can be disposed in separate bins. Or maybe an example can be taken from Africa, where bird rings sometimes get reused for a necklace. Of course, the hunter still has the possibility of reporting the ring, but my confidence in the combination of hunting and science continues to decrease by the day.

São Jacinto ducks: February 6 – 8

During these three days I assisted David Rodrigues (http://www.pt-ducks.com ) again in trapping and marking “patos” at the São Jacinto duck pond. Our captures were reasonable, at least in my opinion, with about 40 or so new Common Teals Anas crecca in our traps, as well as a few recaptures. Additionally, two Little Grebes Tachybaptus ruficollis and two Common Moorhens Gallinula chloropus ended up in our traps, of which only one Moorhen carried a ring. Considering the number of Little Grebes and – Moorhens that have been ringed at the pond during the last months, it was a bit surprising we only got only one recapture among these four birds. I suspect that most of our previously ringed birds were migrants and these are now elsewhere (although some Moorhens may have ended up as Common Genet Genetta genetta food it seemed)  

Most of the Mallards have dispersed by now, which considerably reduced the amount of time we needed to spend on our captures. This gave us to opportunity to clear up the trails from numerous fallen trees and other storm damage. I also trimmed some Acacia longifolia, a fast growing invasive, which after a recent forest fire has almost completely taken over the reserve (https://estudogeral.sib.uc.pt/bitstream/10316/18181/1/HeliaMarchante%20PhD%20thesis.pdf).  Its flowers are very nice, however… 

Although there was not much diversity in our captures, the number of duck species present at the pond was large; especially Eurasian Wigeons Anas penelope and Gadwalls Anas strepera are abundant at the moment, but we also observed an interesting number of Northern Shovelers Anas clypeata, as well as a few Tufted Ducks Aythya fuligula. Unfortunately, none of these ended up in our traps.

A marked Tufted Duck on the left and on the right my first observed marked Gadwall.

 

Eurasian Coots Fulica atra are common in São Jacinto’s ponds and nest there. David informed me their first clutch usually is succesful, but later layers will face low water levels and eventually the stray dogs.

Eirol landfill, February 5, 2013

A somewhat delayed post, but I thought it would be wise to inform you about my most recent visit to the landfill at Eirol (February 5). At arrival there at 9:15am an incredible number of gulls was present, but it was still too foggy to read any rings. After about an hour or so, the fog cleared up and I managed to read 50 rings until about 15:00. These rings had been applied in the following countries: The Netherlands (16 x), Guernsey (13 x), UK (12 x), Germany (2 x), Belgium (2 x), France (2x), Denmark (1 x), Iceland (1 x) and Norway (1 x).

Another mountain under construction...

Two ringed LBBG's of which I can't recall the codes; dirt made the reading of many rings impossible, but at least the bird on the right could be traced back to David Sowter (UK)

 WHITE 1EH, from Gloucester (UK), where it is also a regular landfill visitor, I believe.

 A packed stadium

One of many tibia combos that have been applied in the southwest of The Netherlands, by Roland-Jan Buijs.

 BLACK J0VU, all the way from Norway

The last half hour of my visit was dedicated to an inspection of the present gull carcasses at the site, in particular the ones that were laying at the bottom of the pit (as the landfill only recently opened, a large part of the base of the dump site still consist of bare sand). Here I inspected the remains of 47 Lesser Black-backed Gulls and 12 Black Headed Gulls.

The bottom of a landfill; always worth a visit!

Two metal rings were found; one from the BTO – London, which came from the leg of an adult LBBG that deceased a few months ago, but more interestingly: I also found a metal Lisboa (Portugal) ring around only a single tarsus and foot:



As this particular ring appeared to have the same size as those that are applied on the larger gulls in NW Europe, my first thought was that it would belong to an unfortunate landfill gull. However, there was something suspicious about this situation: the tarsus was obviously too short for a Larus and the orange leg color too different from the leg colors of the gulls present at the site. Additionally, the leg and ring appeared to have been regurgitated by a gull (it was laying among many other gulls’ dietary remains), and as far as I know cannibalism does occur regularly among gulls, but not at the landfill sites I visit. And finally, the ring number appeared a bit too familiar to me... This all made me suspect that this ring had not been applied on a gull, but something else instead. Exactly on what species this ring had been put and how it ended up on the landfill will be presented and discussed in another post soon…