A tiny strip of metal…

By Lauren Gilson & Nic Dunlop.  Who would have thought that one tiny strip of metal could convey so much information? It isn’t a microchip; in fact it is not electronic at all. It is a rather low-tech, simple instrument: the metal bird band.  On a fairy tern (Sternula nereis), this band is 5.5 mm tall by about 8.5 mm wide, if it were flattened,  for a total area of just under 47 mm2.

The marking of birds with imprinted bands is an international research activity regulated in Australia by the Australian Bird and Bat Banding Scheme. In addition to the federally issued, individually numbered band, some birds may also be marked with a plastic colour band, a tape flag, or wing marker. Marking birds allows them to carry information about themselves— their ages, points of origin, but perhaps more importantly, their survivorship— wherever they go. When applied to juvenile birds, colour markers give researchers a window into the timing and patterns of their dispersal.

A cohort of juvenile fairy terns was banded at Rous Head in North Fremantle on 05 January 2016, at a constructed nesting site managed by Fremantle Ports. These birds were outfitted with metal bands, and within three weeks observers were reporting sightings of banded tern fledglings as far away as the Peel Inlet. In some cases, the reports were accompanied by request for identification of the species, because young fairy tern fledglings look quite different from adults.

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A recently fledged fairy tern banded at Rous Head and photographed at Woodman Point 3 weeks later.  This individual still had the rusty face and crown of a recent fledgling.  Photo by Ken Glasson

Terns that were banded at Rous Head on 05 January, still identifiable by plumage as young of this year, were first detected by casual observers at Woodman Point, Munster, WA on 27 January 2016, at a distance of 9.7 km from the Rous Head breeding colony. One month after banding, three banded fairy tern fledglings were observed at Point Walter, Bicton, WA, only 5.5km from the Rous Head colony, and another was detected at Nairns, on the Peel Inlet near the mouth of the Serpentine River on 09 February. This juvenile had dispersed 64 km from its point of origin.

… or a tiny band of plastic

The imprinted information on a metal marker band can only be read once a bird is again in hand, but colour markers may be seen by anyone with a keen eye on the local or migrant avifauna. We were able to identify these fledgling fairy terns as having originated from Rous Head because of their juvenile plumage and the knowledge that the Rous Head population was the only one at which banding had recently been undertaken. In effect, the metal marker served as a colour marker would have done in these cases. Except for this case:

4Q7A6192_Cropped_bluebands
A fairy tern fledgling (left in photo) bearing colour bands on its left leg in addition to a metal band on its right leg that is indistinct in this image.  The paired pale blue colour bands were applied to fairy terns banded on Rat Island in the Houtman-Abrolhos Islands off Geraldton, WA.  Photo by Bob Paterson.

 

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An older fledgling fairy tern photographed at Nairns, Peel Inlet.  The rusty wash is gone from this individual, and the black nape is starting to develop.  Photo by Bob Paterson.

Among the photographs shared by citizen scientists was this image from Nairns, at the mouth of the Serpentine River. The bird on the left is a juvenile, still sporting a dark bill and an incompletely black crown, but the visible bands are light blue, not metal. ‘Ternologist’ Nic Dunlop of the Conservation Council of WA has been applying these blue colour bands in order to track the dispersal of juveniles from islands in the Houtman Abrolhos group off Geraldton, WA. The juvenile fairy tern in this photo was initially thought to have been one of those fledged from the Rous Head colony, but actually originated from the Abrolhos Islands; the Rous Head fledglings were given no colour bands.  This tern had dispersed 470 km from the Abrolhos to the Peel Inlet (the maximum dispersal distance of a fairy tern on record with ABBBS is 516 km, on the eastern coast (according to David Drynan of ABBBS).

IBAs for fairy terns

So how does a tiny strip of metal make a difference?  The constant improvement of digital camera technology has profoundly increased the casual observer’s ability to detect the presence of that tiny strip which might have been indiscernible in the past. The presence of that tiny strip of metal (or plastic) tells an astute observer that someone wants to know something about this organism, which leads to reporting of observations. It also leads to discussion and awareness of wildlife monitoring. Citizen scientists reporting banded birds not only inquired about the birds’ origins, but also reported disturbances to shorebirds by humans and dogs in areas where breeding colonies occur onshore. Making observations and raising concerns with local council and shire governance led to installation of signage and temporary fencing in some areas, to offer the birds some protection from such incursions during their breeding cycles. Growing concern about threats to seabirds along our coasts has led to citizen action, and appeals to city or regional authorities may result in the placement of signage or fencing, at least during these species’ on-shore nesting phase.

Colour markers also enable any observer to provide data about birds to the ABBBS, who will subsequently share those reports with the researcher(s) responsible for marking the birds. For species of concern in Australia, these reports and the actions of local and federal governance may make the difference in maintaining populations that are threatened by urbanisation and anthropogenic predators. Threats to nest fairy terns include foxes, dogs, cats, black rats, gulls, harriers and Australian ravens. BirdLife International’s Species factsheet:  Sternula nereis (2016) reports a 23% decline in population attributable to disturbance and predation, with fewer than 1600 pairs breeding in Western Australia. The species is federally listed as vulnerable in WA.

Important Bird Areas (IBAs) are locations identified by BirdLife International because they support a significant percentage of the world breeding population of a species, or support significantly high numbers of a species at certain times of year, thus are important to protect for the sake of those species that are dependent on them. Western Australia supports 11 Important Bird Areas (IBAs) that support fairy terns (Barrow Island, Carnac Island, Faure and Pelican Islands, the Houtman Abrolhos Islands, the Montebello Islands, the Recherche Archipelago, Rottnest Island, Sandy Island, Lake MacLeod, Yalgorup, and the Pell-Harvey Estuary).

Thanks to Ken Glasson, Toni and Geoff Webster, Bob Paterson for sharing photographs with their local land managers.

Post Script: On 31 March a fairy tern fledgling from Rous Head was recaptured on Rat Island in the Abrolhos Group, 415 km. Nic Dunlop comments that Rat Island may be an important migration staging site for fairy terns.

 

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