Well... results are finally in, and we can report on a very successful colouring marking project of fledgling black-browed albatross form Steeple Jason Island. In April 2003 16 537 young black-browed albatross (Thalassarche melanophrys) chicks were marked with orange paint on their breast, just prior to them fledging.

Young Black-browed Albatross with orange markings at the Steeple Jason colony.

Why This Project is Important

The short-term objective of the project was to collect at-sea sightings of marked birds to determine their dispersal pattern and level of interaction with long-line fishing activity.

We needed to know:

• Where do juvenile black-browed albatross disperse in relation to adult birds?

Our intention is then to use these data to for the development of long-term projects to help target future research into seabird longline mortality on the Patagonian Shelf, including:

• How important is juvenile mortality in the decline of black-browed albatross in the Falkland Islands?
• Are the by-catch rates adults and juveniles comparable?

Population Decline and Dispersion

The Falkland Islands are the most important breeding site in the world for the black-browed albatross, holding 70% of the global population. There is a large amount of evidence that directly links the current decline in this population, and that of many other albatross and petrel species, with longline mortality. There is considerable evidence that longline mortality in Argentina, Uruguay and Brazil, and historically the Falkland Islands has played a major role in the current dramatic decline in the Falkland Islands black-browed albatross breeding population.

While we do know that the majority (up to 97%) of black-browed mortalities recorded in Brazilian waters are juvenile birds there is currently no data on the movements of dispersing juvenile black-browed albatross, sub-adults and non-breeding birds from the Falkland Islands. The fact that relatively few juvenile birds recorded by the Seabirds at-Sea Team (SAST) during at-sea surveys since 1998, and no juvenile mortalities have been recorded by the SAST or Falkland Island Fisheries Department seabird observers on longliners or trawlers operating in local waters in 2001/03, suggests that the issue needs to be addressed over the full extent of the Patagonian Shelf and north into Uruguay and southern Brazil. This suggests that dispersing juveniles generally travel greater distances than adult breeding males and females. We considered it important to gain a thorough understanding of the movements and fate of juvenile birds in order to understand the current decline. Nic Huin's work has identified three possible causes of the current decline in the Falkland Islands: (1) an increase in adult mortality, (2) a decrease in recruitment into the breeding population (i.e. increased mortality of birds aged between 1 and 7-10 years) and, (3) a combination of (1) and (2).

Method Used for Colour Marking Project

Colour marking of albatrosses has been used to identify individual birds and the movement/dispersal of birds from specific breeding colonies The British Antarctic Survey (BAS) has also used the method extensively at South Georgia since the mid 1970's both to study individual birds on land and to research dispersion at sea of birds from known colonies. Each bird was marked by leaning down toward the breast of the bird with the spray can and applying the paint. It was expected that the paint would remain visible for up to 4 months. The advantages of colour marking birds is the cost effectiveness compared to satellite tracking and geolocators, particularly for juveniles which do not return to breed for up to 7 years. The easy identification of marked birds also greatly increasing the potential number of records (sightings) in the short-term, compared with ringing.

We informed at-sea observers of the project throughout the Southern Hemisphere, with observers in South Africa, Australia, New Zealand, Antarctica and South American waters (Argentina, Brazil, Chile and Uruguay). Colleagues in these regions involved with observer programmes assisted by distributing information and data collection forms to at-sea observers, fishing companies and marine tourism operators. Photographs and data collection sheets were also posted on relevant seabird list servers. In Brazil, we worked closely with Tatiana Neves (Projeto Albatroz) and funded several observer trips, in addition Tatiana's team conducted many more trips and worked closely with Dr. Roberto Wahrlich who instructed at-sea observers from the Brazilian Observers Program to record sightings of marked birds between April and August 2002.

To target merchant mariners in the Southern Hemisphere the British Meterological Office assisted by running a story in their quarterly journal the Marine Observer. This is distributed to over 1 200 merchant vessels worldwide. It is estimated that 60 of these vessels have regular trade routes from the UK to South America (via Atlantic coast), Australia (via cape Horn) and South Africa (via Atlantic coast) and up to half would be expected to be in the Southern Hemisphere at any one time.

Project Results

In total, 68 sightings of marked albatross were received. Fifty-eight of sightings were made by observers in Brazil (23 by Projeto Albatroz observers and 34 by Brazilian Observer Program observers), six by a SAST observer south of Mar del Plata on a return trip from the Falkland Islands to Montevideo (Uruguay), a single bird was also recorded by a BAS observer in oceanic waters to the north-east of the Falkland Islands (Figure 1). The majority of sightings were associated with the shelf break, however, this may be a reflection of fishing effort, and therefore the extent of observer coverage. Despite considerable survey effort in Falkland Island waters (including around 140 days by dedicated seabird observers), not a single marked bird was recorded locally. In addition, no sightings were recorded in the southern Patagonian Shelf and no records were obtained in other areas of the Southern Hemisphere.

Sixty-eight records out of a total of 16 537 marked birds equates to a sighting rate of 0.41%. This rate compares favourably with other colour marking projects conducted on black-browed albatross (Thalassarche melanophris impavida) from New Zealand (0.042 in 1995/96 and 0.015 in 1996/97). Considering the enormous area of the Patagonian Shelf and shelf waters of northern Argentina/Uruguay and into Brazil, the sighting rate was considered comparatively high.

Discussion

Satellite tracking of Falkland Island breeding adult black-browed albatross has shown that they feed in different regions of the Patagonian Shelf throughout the year depending on the stage of their breeding cycle. During the incubation period birds forage predominantly in the northern reaches of the Patagonian Shelf (with males concentrated around the shelf break east of Peninsula Valdez and females typically concentrating further north to Rio de la Plata), while during chick rearing, both males and females forage locally in areas adjacent to breeding sites.

On one trip conducted by a Projeto Albatroz observer a total of 2,500 black-browed albatross were recorded, of which 2 499 were juveniles and only one was an adult. On the four days aboard the HMS Leeds Castle outside local waters, a total of 506 black-browed albatross were recorded, of which 476 were adults and 30 juveniles. The vastly different proportion of adults: juveniles in Brazilian and Argentinean waters is further evidence to support satellite tracking data of breeding males and females (Figure 1). As previously discussed, this is also reflected by the fact that 97% of longline black-browed albatross recorded in Brazilian waters are juveniles.

The lack of recorded sightings from Falkland Island waters, despite considerable observer effort, suggests that juvenile birds travel north out of local waters immediately after fledgling. This is further supported by results of at-sea surveys conducted in local waters since 1998, which have recorded very few juvenile black-browed albatross. Due to biases introduced to the data set by the concentration of survey effort in Brazilian waters and to a lesser extent Falkland Island waters, it is more difficult to interpret the significance of the lack of sightings from the southern Patagonian Shelf. The recorded sightings further north in Argentinean waters (around Mar del Plata) in late May and early June suggests that juveniles do not simply pass through the northern reaches of the Patagonian Shelf on their way further north but a proportion of them, at least, use these areas as foraging grounds. Possibly, juveniles pass through the southern reaches of the Patagonian Shelf relatively quickly on their passage north, or pass over the shelf break and oceanic waters further to the east. The single record on the high seas north-east of Falkland island waters is insufficient to support this argument, but it does pose the question as to whether the lack of records in the southern reaches of the Patagonian Shelf is due to juveniles avoiding competition with foraging adult males and females not only by foraging further north, but also by reaching those areas by travelling north by east.

Our results further emphasise the importance of Brazilian waters and the northern reaches of the Patagonian Shelf for juvenile black-browed albatross, and suggests a marked separation between foraging grounds for adult and juvenile birds. Although no longline mortalities of marked birds were recorded the prevalence of juvenile birds in Brazilian waters in combination with their relatively high levels of mortality in this area clearly exhibit the importance of the region for the conservation of the Falkland Islands black-browed albatross population, at least, the high proportion breeding in the Jason Islands. While it is still uncertain what relative importance the mortality of juvenile black-browed albatross has in the currently high level of their population decline it is certain that reducing juvenile mortality in Brazilian waters will significantly increase the number of new birds recruited into the adult breeding population.

Acknowledgements:

This project was run jointly between Falklands Conservation Seabirds at-Sea Team (SAST), Nic Huin (Albatross Studies, FC), Tatiana Neves (Projeto Albatroz, Brazil) and with the support of the Wildlife Conservation Society and Roberto Wahrlich (Brazil). We would to thank the many observers, especially in Brazil, fishermen and merchant sailors without your eyes-at-sea, the project would not have been possible.