Early News Is Good for Shorebirds on Delaware bay
The Early News is Good
Our team trapped over 500 shorebirds over the weekend including several hundred red knots in two catches on May 12th and 14th. Most of the caught birds, knots, ruddy turnstones and sanderlings arrived in good condition, always a relief at this early stage in the season . Ruddy turnstones arrived in better-than-average condition, weighing in at 5 grams higher than normal arrival weights.
The condition on arrival is one of the main bits of information of this work. In some years, knots struggled to get to the bay coming in at average weights of 105 grams, 15 grams lighter than this year. One poor soul practically fell onto the beach with only 84 grams of weight, dangerously burning muscle to get here.
To really understand it best you must put yourself in the birds shoes ( in a matter of speaking). We can do this because we have been attaching small tracking devices called geolocators on knots and turnstones for the last 5 years. Geolocators must be recovered to download the data, and we did this with a knot banded with the inscribed flag TVV in 2015. The map of that bird’s heroic journey can be seen below.
Follow TVV’S path from Delaware Bay to its Arctic breeding area than down to its Chilean wintering area, than back to Delaware Bay. It spent less than one month in the Arctic but over 6 months in its Tierra Del Fuego winter quarters. The rest of the time was spent flying or resting between flights. It’s flight from Southern Brazil to Delaware Bay was truly awe inspiring.
Imagine you are TVV and about to fly from balmy Brazil to Delaware Bay, 5000 miles away. Most birds will leave near nightfall, when the weather is settled and usually with a favorable wind. Once aloft you have no idea of the conditions you will face for the next 6 days. Some birds have an easy time of it, some get caught in opposing winds, other get blown off course and must struggle to return. This is the reason for the varying weights on arrival.
So what did the birds find when they arrived this year? So far the horseshoe crab spawn has gone well. It started early in the month, so that by the time birds like TVV arrived, they found a nice concentration of eggs for the taking Delaware Bay beaches. At first the birds poured into the bay. Last Thursday May 10th we had abut 1000 knots on the NJ side of the bay. By Saturday the number has grown to 8000 knots. And our two catches proved they were gaining weight at a good clip.
All that changed on Sunday when a complicated cold front hit the bayshore. For two days we have had strong winds from the west, creating breaking waves on much of the NJ Shore. The crab stopped spawning in most places. The winds blow as I write this blog and is certainly holding up birds from arriving, some may have stopped migrating others are fighting this merciless 30 mph wind.