Whimbrel Navigates a Storm but Gets Killed Anyway

Machi being fitted with satellite transmitter in August, 2009. Image credit: Barton Paxton

A few weeks ago, I mentioned a migrating Whimbrel that had successfully flown through the most severe portion of Hurricane Irene. There are other Whimbrels tagged by the same monitoring program at the Center for Conservation Biology, which follows the migratory paths of these distinctive shorebirds. Another Whimbrel, named Machi, recently navigated another tropical cyclone, this time Tropical Storm Maria. This story, though, does not have a happy ending for the bird, as it was shot and killed by hunters on Guadaloupe.

Scientists at the Center for Conservation Biology learned today that a whimbrel that they had been tracking via satellite for 2 years as part of a migration study had been shot by a hunting party this morning on the Caribbean island of Guadeloupe (French West Indies).  The bird named “Machi” had just flown through Tropical Storm Maria and made landfall on Montserrat before flying to Guadeloupe.  Machi had been tracked for over 27,000 miles (44,000 km) back and forth between breeding grounds in the Hudson Bay Lowlands of Canada to wintering grounds on the coast of Brazil.  The bird was tracked on 7 nonstop flights of more than 2,000 miles.  During the spring of 2010, Machi flew more than 3,400 miles directly from Brazil to South Carolina.  Machi serves as an example of birds that interact with many landscapes and cultures throughout the year and a reminder of how international cooperation is required for their continued existence.

The center argues that this is a persistent conservation problem on Caribbean islands since many are not subject to the Migratory Bird Treaty Act, which governs the treatment of birds crossing international boundaries in North America.

Guadeloupe, Martinique and Barbados continue to operate “shooting swamps” some of which are artificial wetlands created to attract migrant shorebirds for sport shooting during fall migration.  It is estimated that tens of thousands of shorebirds continue to be taken annually by hunting clubs on just these three islands.  This practice is a throwback to more than a century ago when gunners hunted shorebirds throughout the Americas.  The Migratory Bird Treaty Act was passed, in part, to protect dwindling numbers of birds that migrate across country borders.  Operated as a French overseas department, both Guadeloupe and Martinique are part of the European Union and are not party to the Treaty.  Barbados, once a British colony is now an independent state and also not party to the Treaty.  The last Eskimo Curlew known to science was shot on Barbados in 1963.  Shorebird hunting within these areas continues to be unregulated to the present time. Conservation organizations continue to work toward some compromise that will reduce pressures on declining species. 

Worldwide, many shorebird populations are experiencing dramatic declines.  Most of the migratory shorebird species breeding in eastern North America and the Arctic pass over the Caribbean region during the late summer and early fall on their way to wintering grounds.  When they encounter severe storms the birds use the islands as refuges before moving on to their final destinations.  Hunting clubs take advantage of these events and shoot large numbers of downed birds following the passage of these storms.  During the 2009 and 2010 fall migrations, Machi did not stop on any of the islands but flew directly from Virginia to Paramaribo, Suriname before moving on to winter near Sao Luis, Brazil.  It appears that the encounter with Tropical Storm Maria caused the bird to stop on Guadeloupe.

This comes from the press release about the incident, which may be downloaded here.

Tracking map of Machi (2009-2011).  Image credit: The Center for Conservation Biology.

Update: It turns out that a second tracked Whimbrel was also shot there on the same day (pdf). BirdLife and other conservation organizations, including the Society for the Conservation and Study of Caribbean Birds, are calling for better regulation of hunting in the Caribbean to avoid killing species of conservation concern.

Local Shorebirding

While Hurricane Irene did not bring me any tropical birds, it has created some good opportunities for local birding. The Raritan River flooded on Sunday and remained flooded on Monday, with the waters gradually decreasing since then. At this point, the flooding here is finished, but the river's level remains very high, so that areas that are normally exposed at low tide are still submerged. This leaves waders that depend on tidal mudflats looking for new locations for foraging and loafing. Meanwhile, with the river still high and the ground still saturated, a lot of fields have big wet areas.

One of the open areas by the old basketball courts in Donaldson Park was still flooded as of Thursday when I made my last visit there. More birds were using the wet area than I initially thought. There were a few dozen Mallards: some swimming and some roosting on the branches that had fallen in that area. When I walked around to get a closer view from the other side, I could see that there were many more birds than I initially thought. There were at least two dozen peeps (Least and Semipalmated Sandpipers – no Westerns that I could see), plus a few larger sandpipers (Solitary Sandpiper, Spotted Sandpiper, and Lesser Yellowlegs). None of these shorebirds are particularly rare, but seeing so many at once in this location is highly unusual.

Lesser Yellowlegs is probably the yellowlegs I see less frequently in New Jersey. I'm not sure if this reflects an actual distribution pattern or if it is just an impression.

Solitary Sandpiper is actually one of the more reliable sandpipers at Donaldson Park. Least Sandpiper is the sandpiper that one is most likely to see there. After that would come Spotted Sandpiper and Solitary Sandpiper. The Solitary Sandpipers that visit Donaldson Park seem to prefer the wet fields to the edges of the river, unlike the Spotted Sandpipers, which I usually see along the riverbank. This wet area was one that both could agree on. Contrary to its name, this Solitary Sandpiper was not solitary, as one or two others were nearby.

The floodwaters have receded, but there is still evidence of the torrents all over the place, with a few trees down, fences covered with debris, and even one bent fence.

Birding the Middlesex Coast

Elsewhere in the Garden State, birders were delighting in a rare sighting of a Brown Booby in Jarvis Sound near Cape May. The booby was seen by the naturalists aboard The Osprey, a pontoon boat that runs daily birding excursions during the warmer months. I have taken several trips on that boat, and none of them turned up any birds that exciting!

Great Egret in a tree

I only found out about that rarity after returning home from an excursion to the Middlesex County portion of Raritan Bay. The first stop was at South Amboy's Morgan Avenue mudflats. As usual, there was a squad of Great Egrets perched in a small grove of trees close to the beach. The egrets were joined by one immature Yellow-crowned Night Heron. When I turned to keep walking along the beach, I saw two dark, spindly birds in flight over the marsh. I found them with my binoculars, and they turned out to be two Glossy Ibises. They circled a few times before finally settling somewhere in the marsh.

Yellow-crowned Night Heron

As I continued out towards the spit, I could see a man with a metal detector walking around out on the beach. He walked out along the spit to cross the creek, close enough to the hundred or so birds gathered there to flush all of them. By the time I got out to the spit, there were few birds around, and most of those were in flight. I started looking at the many Osprey, and I was looking at one, two light-colored birds passed through my field of view. When I got on them, I saw that they were two Caspian Terns – heavy-billed for terns, with a dark cap extending from their bills to the backs of their heads (unlike Royal Tern at this time of year).

Semipalmated Sandpiper

The second stop was at Pirate's Cove. Here again, the birds on the sandbar got flushed. Despite that, there were some Semipalmated Sandpipers and Semipalmated Plovers along the shoreline, and it was possible to get fairly close without flushed them. One Ruddy Turnstone flew back and forth a few times, and Common and Least Terns were both present.

Semipalmated Sandpipers

A third stop at Cliffwood Beach Park, just over the creek from Pirate's Cove, turned up the same set of birds as at Pirate's Cove. There is a short section of boardwalk that might provide a good viewing point for someone with a spotting scope. The beach running west from Whale Creek was mostly unproductive, though there was a nice collection of terns near the Laurence Harbor end.

Migrating Shorebirds on Raritan Bay

Yesterday morning I was out on Middlesex County's Raritan Bay coastline to see what sorts of waterbirds might be moving through. Even though it was not as hot as a few weeks ago, the heat affected me more than I expected, so that I felt a little sick at times. As a result, I did not spend as much time on the beaches as I otherwise might have and probably saw fewer bird species.

The first stop was the mudflats at Cliff Avenue in South Amboy. As usual, the spit was lined with birds, most of which turned out to be common gulls (Laughing, Ring-billed, Herring, and Great Black-backed). A few terns, mostly Least and Common, rounded out the numbers. Two Black Skimmers skimmed just offshore, sometimes in tandem and sometimes separately. A few shorebirds were about, particularly Willets and Greater Yellowlegs. Two Spotted Sandpipers were working the high tide line on the beach. The most impressive sight, though, was the large aggregation of egrets. At least fifteen Great Egrets were perched in a grove of trees; a few are shown above. A similar number of Snowy Egrets worked the shallow water just off the beach. Among them were two Little Blue Herons (a new county bird for me) and one Great Blue Heron.

The second stop was Pirate's Cove in Cliffwood Beach. I was no sooner in the parking lot than I saw a stocky heron fly up out of the near side of the creek, over the road, and land on the other side. Immediately sensing what it was, I crossed the road and found the bird standing on the west side of the creek – a juvenile Yellow-crowned Night-Heron, my second county bird for the day.

The beach itself had a similar assortment of species as the South Amboy mudflats. One new species for the day was Boat-tailed Grackle; a few were out on one of the sandbars. Pirate's Cove provided a better viewing distance of Common Terns and Willets than South Amboy did. Flocks of terns right now show a mixture of adults and juveniles. One juvenile yesterday was begging nonstop, letting anyone who would listen know about how hungry it was. Most of the terns around it just kept preening or resting. Its parents were out catching fish and brought back an occasional morsel to feed it.

Study Confirms Importance of Red Knot Migratory Stopovers

As many readers know, Red Knots (Calidris canutus rufa) are in serious trouble.* Though they were once an abundant shorebird during spring migration on the Atlantic Coast, their population crashed in the 1990s. This winter, Red Knots suffered another setback, when a third of their current known population disappeared from the wintering grounds for reasons that are not entirely clear. The major crash in the 1990s has long been linked to food availability at migratory stopover sites.

During spring migration, Red Knots time their arrival in the Mid-Atlantic to coincide with the spawning of horseshoe crabs. Red Knots (and other shorebird species) eat the freshly-laid eggs to gain weight for the final leg of their journey, from the Mid-Atlantic to the Arctic, where the birds need to find mates and breed within a fairly short window of time. A major increase in the harvest of horseshoe crabs, due to their increasing use as bait for whelk fishing, reduced the availability of horseshoe crab eggs. While some shorebird populations remained stable or suffered small decreases, the Red Knot population crashed.

A new study, published in the open access journal Ecosphere, confirms the importance of stopover habitats – and the food sources they provide – for migratory shorebirds. The study uses data collected during a multiyear banding project of shorebirds around Delaware Bay. (As readers may remember, I participated in one such banding session earlier this year.) The study used two types of data from the project: captured or recaptured birds with known identities and known weights and resighted birds with known identities but unknown weights. The project has been banding Red Knots and other shorebirds with metal bands since 1997; in 2003, it started tagging Red Knots with colored bands bearing alphanumeric codes that can be read with binoculars or a spotting scope.

The study used mathematical models to determine the relationships between spawning by horseshoe crabs and weight gain by Red Knots and between Red Knots' mass at departure and future survival. (You can read the study's methods section for a technical description of the models.) The results showed that how much weight Red Knots gain depends not so much on the overall horseshoe crab abundance but on the timing of horseshoe crabs are spawning. If horseshoe crabs spawn later than usual, Red Knots are not able to gain as much weight as they normally would because not enough eggs will be available before they have to depart for the Arctic. Weight gain at stopover sites is crucial since Red Knots with a light weight at departure were unlikely to be recaptured or resighted in subsequent years.

While the model found a correlation between weight gain and subsequent survival, it found a stronger relationship between survival and snow depth on the Red Knots' breeding grounds. Red Knots were more likely to survive from one year to the next if there was deeper snow on the ground when they arrived in the Arctic. The scientists offer several possible explanations. One is that greater snow depth means greater overall moisture, which increases the amount of invertebrate prey available for the Red Knots. Another is that lemming populations tend to crash in years with low snow depth, so in those years predators that normally eat lemmings might turn to shorebirds instead. Determining whether those or other hypotheses are correct will require further research in the Arctic.

The study reinforces the link between horseshoe crabs and Red Knots and the importance of Delaware Bay as a spring stopover site. All necessary efforts should be taken to ensure that the bay continues to provide adequate habitat and food for these long-distance migrants. Such efforts should include further restriction of horseshoe crab harvests, particularly in Delaware, which has continued to allow harvesting even though New Jersey has imposed an indefinite moratorium.

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Cited study:
McGowan, Conor P., James E. Hines, James D. Nichols, James E. Lyons, David R. Smith, Kevin S. Kalasz, Lawrence J. Niles, Amanda D. Dey, Nigel A. Clark, Philip W. Atkinson, Clive D. T. Minton, and William Kendall. (2011). Demographic consequences of migratory stopover: linking red knot survival to horseshoe crab spawning abundance. Ecosphere, 2 (art69) : 10.1890/ES11-00106.1

* For international readers, the IUCN ranks Red Knot as a species of least concern; the discrepancy is that there are multiple subspecies, and many of them are secure. However, the western Atlantic subspecies – the one that breeds in the North American Arctic, migrates along the Atlantic Coast of North America, and winters in Tierra del Fuego – is in serious danger of extinction.

Some More Shorebird Photos

These are a few additional photos that I took on Saturday, but that did not fit into my post on shorebird banding yesterday. Up above, a group of Dunlin pause in the surf, with a Semipalmated Sandpiper standing by.

A Dunlin forages in the foreground while Red Knots stand in the surf.

A familiar trio from Reed's Beach: Red Knot, Laughing Gull, and Dunlin.

A Semipalmated Sandpiper picks through beach litter for morsels.

A Laughing Gull stands in the surf.

Speaking of Laughing Gulls, this is what Reed's Beach looked liked on Sunday morning. Cape May County has one of the largest Laughing Gull breeding areas in the world in its back bay marshes along the eastern side of the peninsula. Apparently a lot of those nests got flooded out in the last week because of recent high tides, made higher than normal by their proximity to the full moon on Tuesday. As a result, a lot of those gulls were hanging out in the horseshoe crab spawning areas along the Delaware Bay instead of tending to their nests in the marshes.

Shorebird Banding in Cape May

As many readers are aware, conservation of shorebirds that use the Delaware Bay as a migratory stopover is a pressing issue. Many species, such as Red Knots and Ruddy Turnstones, time their migration to arrive at the bay just as horseshoe crabs are laying their eggs on the beaches. Shorebirds feed on those eggs to regain the weight they lost during their flights from wintering grounds in South America and prepare for another long flight to their Arctic breeding grounds. For a long time this arrangement worked well, but in the 1990s, overharvesting of horseshoe crabs (used for fishing bait and medical research) caused a crash in the Red Knot population. States have taken some steps to limit the horseshoe crab harvest (including New Jersey's legislative moratorium), but the Red Knot's survival remains tenuous. The population has fallen enough to earn the Red Knot a place on the USFWS's candidate list but so far it has not been listed as threatened or endangered by the federal government.

An international effort is underway to monitor the remaining population and push for conservation of the habitats and resources the Red Knots need. Part of that is an ongoing banding program to study how birds use stopover sites and what migration routes they use. My friend Mary (whom I met through DC Audubon) knows some of the banders from her time in Australia, so she got invitations for the two of us to participate in a banding session this past weekend. Because of weather and tides, it turned out that Saturday was our best chance to participate, so we made sure to be at Reed's Beach early in the morning, even though we both arrived in Cape May rather late the previous night.

You can see how shorebirds are banded in a video I linked on this blog a few years ago. That shows a different set of banders in a different location, but the methods for capture and processing are essentially the same. The banding team prepares a net and disguises it as carefully as possible. Once enough shorebirds are in front of the net, the team fires cannons that propel the net over the birds. Some birds will escape, but many will be caught under the net. The banding team hurries to extract the birds from under the net as quickly as possible, so as to avoid unnecessary stress or injuries to the birds. Once all the birds are out of the net and into shaded containers, the banders can sit down and process them.

On Saturday, the captured birds went through several steps before their release. First they were banded and marked with coded tags to make it easier to recognize individuals in the field without recapturing them;* then a series of measurements were taken: weight, wing chord, and bill and head length; finally, feather samples were taken for lab analysis. One person recorded all of the codes and measurements for each bird. I was last in line, so I held each bird while another person snipped some feathers (one wing covert and two breast feathers), and then I released it. I think I probably handled a few dozen Red Knots in the course of the morning, though I was not keeping count.

It was really cool to hold the Red Knots and see them up close. One thing I had not realized when I looked at them through binoculars was just how intricate the patterns on their backs are. Their scapulars in particular have dark brown lines dividing each feather into sixths; the middle part of the feather is tinged with rufous while the tip is white. Meanwhile, their rumps are etched with fine barring, and their undertail coverts are speckled. The Red Knots were also smaller than I expected; I guess they look larger to me through binoculars than they do in the hand. A lot of these birds were recent arrivals, though, so it is possible I would get a different impression once they had time to gorge themselves on horseshoe crab eggs.

As I mentioned in yesterday's post, Mary and I went to Heislerville in the afternoon and evening to find a Curlew Sandpiper. Once we had found it, we helped with another banding project that is monitoring some of the species using the impoundments. That project is mainly concerned with Semipalmated Sandpipers, but it also bands Short-billed Dowitchers, Dunlin, and other shorebird species that happen to get tangled in the nets.  Mary helped extract shorebirds from the nets, while I ferried birds from the nets to the banders or held nets so that they would not blow on a bird during the extraction process. Once again I was impressed by the birds' small size; the Semipalmated Sandpipers were especially tiny.

I really enjoyed my experience with shorebird banding this weekend, and I hope to do more of it when I have the chance.

* If you happen to see a Red Knot (or other shorebird) with color markings or a colored flag with an alphanumeric code on it, please report it to bandedbirds.org.

Seeing a Curlew Sandpiper

This past weekend I was in Cape May, primarily to participate in shorebird banding, but also to see any rare birds that might be around. I was especially eager to see one of the several Curlew Sandpipers that have been frequenting the impoundments at Heislerville. This is a species I have missed on past visits to Heislerville. Plus, who can resist a sandpiper with a long, down-curved bill and a bright red breast? Not me!

During migration seasons, Heislerville attracts thousands of shorebirds, especially at high tide. As the tide rises, more and more shorebirds fly in from nearby feeding areas along the Delaware Bay and its tributaries. On Saturday evening, there were probably 10,000 or more in the main impoundment by high tide. From what I could see, the plurality were Dunlin, but there were substantial numbers of dowitchers and peeps as well. The shorebirds feed and rest a short distance from the dike, which allows for excellent views of these common shorebirds.

One of the other birders present announced that the Curlew Sandpiper was foraging in an exposed area with some of the peeps. My friend Mary found it in the scope before I found it with binoculars and let me have a look at it. The bird was a bit paler than I expected, but its bill was obviously down-curved and its overall pattern was noticeably different from other, more common shorebirds. It was convenient to have Dunlin and Short-billed Dowitchers nearby for comparison.

One other species of interest in the main impoundment was Red Knot. A group of about ten was among the thousands of other shorebirds. One of the group was banded and wore a light green flag with the code 3CP. By entering the code at bandedbirds.org, I found out that this bird was banded at Mispillion Harbor in Delaware in 2009 and was recaptured at Kimble's Beach in New Jersey in 2010. That means that this individual has made it back to Delaware Bay three years in a row as part of its annual round trip from southern South America to the Arctic and back.

Robins and a Snipe

Yesterday I visited the Negri-Nepote grasslands for the second time in two weeks. This time the fields were a lot quieter, without the small flock of Tree Swallows that I had noted last time. What was notable was the number of American Robins, which were present in several large flocks. In the photo below, you can see 20 robins, and that was only a portion of their number.

Besides the robins, there were three American Kestrels, two Northern Harriers, and a Red-tailed Hawk patrolling the fields. A few Eastern Bluebirds seem to be setting up breeding territories in the fields. Beyond that, the preserve is still waiting for the influx of spring migrants and summer residents.

On Thursday, another birder found a Wilson's Snipe in Johnson Park, with further reports of the bird on Friday. So yesterday I went over to follow up since it would be a county bird for me. Sure enough, the snipe turned out to be easy to find, as it was hanging around the same drainage ditch where it was reported for the previous two days.

A couple of Mallards hanging around nearby provided a nice size comparison for the snipe.

Dunlin at Barnegat Light

The last time I was at Barnegat Light, there was a large flock of Dunlin camped out on the jetty. Some were foraging, but most were huddled wherever there was shelter from the howling wind. The uneven surface on the top of the jetty makes walking difficult, but it provides plenty of depressions where shorebirds can take shelter.

I estimated that there were about 180 spread over the top and sides of the jetty. This is a small portion of the flock. This group did not want to move when I approached to pass, whether because they are used to foot traffic or because they did not want to give up their sheltered roosting places.

Meanwhile, other Dunlin were feeding among the mussels attached to the rocks.

The many mussel beds along the sides of the jetty made it easy to understand why so many waterfowl and shorebirds were gathered in the location.

Here are some of the Dunlin with a Purple Sandpiper in their midst.

Ruddy Turnstones at Barnegat Light

Beautiful sea ducks are the main reason so many birders visit Barnegat Light in the winter, but they are hardly the only birds to watch. The inlet's jetty also hosts a fair number of shorebirds. Five species predominate: Purple Sandpiper, Ruddy Turnstone, Dunlin, Sanderling, and Black-bellied Plover. When I was last at the jetty, I did not see any Sanderlings, but there is usually a flock on the beaches there. (Perhaps they had flown across the inlet to Island Beach State Park.) All the rest were present, with Dunlin outnumbering the rest. I will have a post on them later in the week.

I saw relatively few Purple Sandpipers (normally a highlight at Barnegat Light) or Ruddy Turnstones on my last visit there, but both were on the jetty. In winter, Ruddy Turnstones lose the ruddiness that gives them their name, but they retain the distinctive bib and moustache. Ruddy Turnstones are one of the northerly breeders among shorebirds, with their breeding range covering parts of Nunavut and Greenland, as well as the northern coasts of Alaska and Siberia. Their winter range extends along the Atlantic and Pacific coasts of North and South America.

Here is a Ruddy Turnstone with a Purple Sandpiper. It is easy to see why shorebirds winter here, with a convenient mussel buffet. Turnstones switch from eating flies and other insects to a more varied diet in winter. Crustaceans and mollusks are their main prey items, but they also will scavenge animals killed by other birds and refuse left by humans. Speaking of refuse, the gray item in the lower right of this photo appears to be a fishing weight.

Sandpipers on the Rocks

On Monday I was at the Avalon jetty during heavy fog. The fog was so thick, in fact, that the regularly-scheduled seawatch had been called off for the morning. It would not have done any good to have the counter there since it was barely possible to see birds near the jetty, much less birds migrating past the jetty. It was much easier to see the shorebirds running on the jetty itself. Most of them were Purple Sandpipers, such as the one above.

The Purple Sandpipers were feeding in some of the pools that formed after a wave hit the jetty. I am not sure exactly what they were finding to eat there, or if they were finding anything in the pools. Perhaps the waves carried some small animals onto the rocks.

Others were working the edges of the jetty, but they had to run for cover whenever one of the larger waves crashed.

The were also Ruddy Turnstones, like the one above. These moved  faster than the Purple Sandpipers, so they were harder to photograph, even though sometimes they ran right past my feet.

Most of the Sanderling were on the beach, but one ran up on the jetty.

Avocets at Brigantine

American Avocets are regular visitors to New Jersey in warmer months, especially late summer. They show up frequently enough that one can expect a few to show up around southern New Jersey's coastal hotspots, but not often enough for birders to take them for granted. With their elegant bodies and thin, upward-curving bills, it would be hard to tire of them even if they were far more common here.

This small flock has been lingering at Forsythe NWR (a.k.a. "Brigantine"). Sightings of this species in colder months are somewhat unusual, so these birds may not stick around much longer. When I first saw them, they were wading into deep water – so deep that it came up to their chests. They almost appeared to be swimming.

Migrating Shorebirds May Use Food from Stopover Sites for Egg-laying

Since migration and egg production both require a significant amount of energy, it was uncertain whether long distance migrants used all of the food they consumed at stopover sites for migrating (and used food from the breeding grounds for egg production) or whether they used some for migrating and some for egg production. The question now appears to have an answer, at least for Pectoral Sandpipers. Sandpipers that arrive early at the breeding grounds use energy stored from stopover sites, and birds that arrive later eat to produce eggs.

By means of an isotope ratio mass spectrometer, the scientists studied different isotopes in the diet and the tissue of the birds to determine the origin of the accumulated resources. Using the distribution of stable carbon and hydrogen isotopes they could reveal when those elements had been incorporated through the diet. First, it was found that the values of the stable carbon isotope C13 in blood plasma of females, but also in feathers and claws, were different from those of their chicks. Moreover, the chick values showed an isotopic signature that was clearly different from the local diet.

From this observation the researchers concluded that the resources for egg formation could not originate from nutrients of the breeding area. Interestingly, isotopic values of female red blood cells matched those of the offspring, suggesting that resources were acquired somewhere along the migratory route. The wintering site as origin could be excluded, because in this case the red blood cell values should correspond to those of claws and feathers (assuming that birds moult in the wintering site). "The stable isotope analysis allowed us to confirm the hypothesis that body stores of migrating sandpipers are acquired at stopover sites along their migratory routes. This finding emphasizes the importance of these stopover sites for the well-being of the population", explains Bart Kempenaers, director at the Max Planck Institute for Ornithology in Seewiesen.

The data analysis revealed another surprising result. As the breeding season progressed, the isotopic values of females and chicks became more similar to those of the diet. This means, females that started egg laying later in the season mainly used dietary items from the breeding site, such as crane fly larvae and oligochaetes, as resources for egg production. "It suggests that pectoral sandpipers adopt different strategies for resource allocation according to their arrival time and the start of breeding", argues Elizabeth Yohannes, first author of the study.

But the question remains why some birds arrive earlier than others. Again, this could be answered with the help of stable isotopes. When the researchers analysed the hydrogen isotopic composition from feathers of female pectoral sandpipers, they found that these values corresponded closely to those of precipitation in northeastern South America. Presumably, birds overwinter in different areas (where they also moult their feathers), and those that start off from northern South America migrate shorter distances and therefore, arrive at the breeding ground in Alaska earlier than their conspecifics that start further south. However, details on the routes and timing of migration, and whether the different breeding strategies have an impact on the reproductive success of pectoral sandpipers are still unknown.

Shorebirds at Sandy Hook

There were lots of birders at Sandy Hook yesterday, perhaps inspired by the news of favorable weather for migration. I did not see many warblers (only 5 species), but it was clear that there was substantial movement last night. There were dozens of Yellow-rumped Warblers, particularly along the Fishermen's Trail near the hawk watch bunker. At Plum Island, the birds were changing over to a winter cast – Ruby-crowned and Golden-crowned Kinglets, White-throated Sparrows, and my first Dark-eyed Junco of the fall. Out on the beaches, most of the Laughing Gulls have moved on, and large flocks of Herring Gulls, Ring-billed Gulls, and Great Black-backed Gulls are taking their place. Winter waterfowl are not present in significant numbers yet, but it is only a matter of time until they are.

I enjoyed spending some time with the Sanderlings and Black-bellied Plovers at the end of the Fishermen's Trail. Sanderlings tend to cluster along the ocean's edge. As a wave recedes, they chase it to feed in the newly washed sand, and then they run back up the beach as a new wave breaks. When not feeding actively, they often loaf just a few feet from the waterline, as these Sanderlings are doing.

The dry spit where they were resting cannot have been very wide, perhaps two feet, with water on both sides.

As I was watching and photographing the Sanderlings, five Black-bellied Plovers flew in to join them. The birds all cleared away when a wave (probably amplified by the wake of a passing boat) washed completely over their resting spot.