Written by Brad Winn/Manomet Center for Conservation Sciences
Success! Another geolocator in hand. Our second tagged bird proved more elusive than the first. Though initially interested in the playback from the phone, he would not come close to the bow net. The constant wind whipping over the tundra also made a stationary mist net impractical. We settled in to observe the behavior patterns and routine of the bird banded with the colors Orange-White-Orange, our geotagged sandpiper.
Semipalmated Sandpipers are generally not very wary of humans on the nesting grounds, and Orange-White-Orange was no exception. Very quickly he allowed us to approach to within a few meters when foraging around his favorite ponds. Our winning solution to capturing him was a slow and patient stalk while holding a mist net between us. Our strategy was complicated by the lumpy tussocks and mounds that cover the wet tundra. The first time we dropped the net on Orange-White-Orange, he was able to sneak out the side between two tussocks. Fortunately, he did not seem to realize that we were responsible for his near-capture, and he allowed us to approach closely again. This time we chose a relatively open area near the edge of a pond and waited for him to forage his way into the catch zone. Working in close coordination, we flipped the net over the little sandpiper and seconds later had him in hand!
Wrybill is a very naive bird. It evolved in New Zealand when there were no introduced mammalian predators and consequently it has no appropriate behaviour to respond to the threats of predation. It is not the least bit shy when it comes to human beings either. When it comes to cannon netting this is a good feature! At Pukorokoro Miranda a significant proportion of the New Zealand, and also the world population overwinters. Other northern harbours, particularly the Manukau have overwintering populations. The birds arrive at Pukorokoro Miranda when the South Island breeding season is complete, around Christmas time. There are always non-breeding birds present at Pukorokoro Miranda any time you visit.
On 21 June over 500 Wrybill were caught using cannon net by a team of volunteers and researchers.
It is in the South Island breeding sites that the species is at greatest threat. Braided river systems carry water from the mountains and, at low flow braids of flowing water are separated by large areas of rocks and gravel derived from the Southern Alps. These areas are where the bird breeds and it is ideally camouflaged to avoid visual detection. Ideally peak flow events prevent vegetation becoming established. Mammalian predators hiding in this vegetation are the major threat to nesting birds, second to this 4WD vehicles using the wide expanses for recreation.
Controlled water flows resulting from hydro schemes and reduced flow due to water extraction result in conditions that cause vegetation build up. Some rivers do still remain where the scouring effects of seasonal flood events keep the braided rivers in peak condition. However, this is a species that now depends upon human management for its long term survival.