Expedition to the Arctic: Red Knot – June 28, 2003
The north esker was our last to be searched. It lies along two lakes running perpendicular to the main esker, approximately 3 km north. Last year we found one nest on the esker and a second just off the esker less than 1km away. As described last years journal we tracked both pairs with transmitters. It was a unique opportunity to visit their daily lives, one incubating for 12 hours at a time, the other flying far from the nest to feed, probably to the ocean coast 10 km away. We learned first hand the complicated natural history of this elusive bird, defining territories, evading predators, tending nests.
Our preoccupation with the two pairs led us to more birds in the area. In one centrally located wetland we watched knots from at least 4 different pairs in the area. We saw more knots in that area than any other area that year calling, flying and interacting with one another with the effect of confusing all of us as to what it all meant.
And then we left. But against all odds we had a new contact with these birds, this time on the Delaware Bay. Phil Atkinson, of the British Trust for Ornithology team in Delaware, captured a white flagged bird feeding on horseshoe crab eggs in Mispillion Harbor. The metal band number identified it as the female of the pair nesting on the North esker. Although it has been suggested that the female tends to move each year the second female of the two North esker pairs turned up as one of the two pairs we found this year on the main esker.
This year we searched the north esker area hard, even doubling the search area, to reduce our chances of missing the nest. Still we found no nests and we saw or heard no knots in the area. Later in the evening I ran point counts in the area of both nests but failed to hear a single knot calling.
Our failure to connect with these knots on the north esker provided us with clear corroboration of our overall impression that the knots have faced a significant decline in the last year. Four years ago we watched and heard many knots displaying, feeding and nesting all around the the north esker. Now there were none
And then there is the fate of 9822-03310, the knot resighting in the Delaware Bay. On one hand it may have moved to another location as females tend to do but then other female of the north esker moved only a short distance to become one of the three pairs we did find this year. It was recaptured on the Delaware Bay so it couldn’t have been lost south of the bay. It hadn’t reached suitable departure weight on the bay at the time of capture, did it? If it didn’t, as we suspect many birds did not did it try to make the arduous flight to the Arctic without being properly prepared.
What would have happened if it did attempted this flight? It could have stopped short exhausted and turn around to begin a southbound flight early. It could have completed it’s flight and arrived in the second week of June just as the land began it’s yearly thaw and invertebrate prey were unavailable. Without prey it would have to rely on fat accumulated from gorging on horseshoe crab eggs of Delaware Bay. But without this fat it could have failed to breed and moved on succumbed to the normal effects of poor nutrition, death in the jaws of an arctic fox, or the talons of a snowy owl.
For knot there are more possibilities. Theunis Piersma of the Netherlands Sea Institute has found that before they leave the bay, the red knot reduces it’s organs of digestion (stomach intestine) while increasing the organs of flight (heart lungs) only after it reaches a suitable weight of about 180 gms. This helps them fly to the Arctic, but also forces them to survive of stored fat as they reverse the process and alter their physiology back to normal. Theunis suggests the without that fat they may not be able to make the transition and the metabolic stress could be fatal. We can only wonder what happened to 9822-03310.