Shorebird populations worldwide are declining and their habitats are under stress from human factors including global climate change. To underpin the conservation of the migratory shorebirds that connect us all, GFN aims to foster and conduct global cooperative ecological and demographic research. Initially our efforts will focus on flagship species such as the Red Knot and the Bar-tailed Godwit.
In 2001, Allan Baker of the Royal Ontario Museum, Theunis Piersma of the University of Groningen and the Royal Netherlands Institute for Sea Research (NIOZ) and Phil Battley of Otago University designed an ‘umbrella’ for international co-operation and fund-raising for global flyway research, the Global flyway Network. So far, the Gobal Flyway Network has been an informal, but highly effective, platform for developing initiatives towards effective research that strengthens the conservation status of migratory shorebirds.
Globally, shorebird populations are declining, but for most populations current monitoring is insufficient to diagnose causes or predict future trends. Increasingly tight timing along a migration route and physiological costs during migration mean that changes in habitat quality and availability (e.g. reclamation, natural or human-induced food shortage, hunting pressure) put shorebird populations under extreme pressure. The use of only a few, essential, stopover sites means that entire populations or subspecies can be at risk. A recent conference of the International Wader Study Group (Cadiz, Spain, September 2003) concluded that there is strong evidence for population declines in many species of wader and stressed the need for internationally coordinated research initiatives into the population biology of migratory waders. These issues are of urgent conservation importance.
Scientifically, determining how different migration strategies infuence the seasonal and annual survival of shorebirds is an important step towards understanding how these strategies evolved and are maintained. The strongest tool in these investigations is by investigating the comparative demographics of different subspecies on a global scale. This is what we are attempting with Red Knots and Bar-tailed Godwits.
These issues require demographic monitoring of shorebird populations, beyond simply counting birds. Counts, while valuable, contain errors that are not readily identified, and cannot reveal the cause of population change, or the future population trend. Survival analyses using mark-recapture statistics are the key to understanding both the biology and the conservation status of populations. These allow construction of population models that can reveal whether population processes are similar between different populations, and whether these populations are stable, decreasing or increasing. This type of monitoring is often most easily undertaken on the non-breeding grounds.
The importance of this approach is evident in the Americas, where an intense banding effort in Argentina, Chile and Delaware Bay, USA, has revealed how a population collapse in the rufa subspecies of Red Knots can be attributed to overfishing of horseshoe crabs Limulus polyphemus at the single key stopover site (Delaware Bay) (Baker et al. 2004. Rapid population decline in red knots: fitness consequences of decreased refuelling rates and late arrival in Delaware Bay. Proceedings of the Royal Society of London B 271, 875–882).
Detailed colour-marking and resighting programmes are underway or about to be initiated on all the six subspecies of Red Knot (in Europe [islandica], West Africa [canutus], NW Australia [piersmai], New Zealand [rogersi] and the Americas [rufa and roselaari]), and the four generally-recognised subspecies of Bar-tailed Godwit (in Europe [lapponica], West Africa [taymyrensis], NW Australia [menzbieri] and New Zealand [baueri]. Studies in NW Australia are also being made on the Great Knot, a related species that is intermediate in body size between Red Knots and Bar-tailed Godwits. This species is of special concern in the East Asian-Australasian Flyway, as one of the key stopover sites on migration, Saemangeum in South Korea, is currently being reclaimed in the single largest land claim development in the Yellow Sea. (Click here for information about Saemangeum on Birds Korea)