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Posts Tagged ‘International Migratory Bird Day’

Creek Mouth Shoals Provide Key Habitat During a Cold May

Monday, May 23rd, 2016
One of a Series of Updates on the 20th Year of the Delaware Bay Shorebird Project

by Dr. Larry Niles, LJ Niles Associates LLC

In spite of the very spotty horseshoe crab spawn, the shorebirds on Delaware Bay seem to be gaining weight on schedule. Below you will find a graph composed of the average weights of all the red knots by our team for the last 20 years. The curve is the result of combining all the data we collected and shows the sweet spot for most knots. As they arrive, they take time to gain weight but after about 5 days they start gaining weight rapidly. After the 26th or so, birds start reaching the critical weights necessary to safely reach the Arctic breeding grounds. One can see the curve deep at the end of the month because fat birds fly off leaving the less fat behind. In general, weights above the line are good, below the line not good. The large squares on the graph are the average weight of this year. So far, so good.

Average Red knot weights from catches made in 1997 to 2016. The most recent are the big squares. So far average weights are following normal pattern of weight gain.

Average Red knot weights from catches made in 1997 to 2016. The most recent are the big squares. So far average weights are following normal pattern of weight gain.

Cannon net firing over red knots on Delaware Bay

Cannon net firing over red knots on Delaware Bay

This is a bit of a surprise for the team. The weather here on Delaware Bay is wet and cold. The water temperature struggles to lift above 59 degrees, the temperature necessary for a crab to spawn on Delaware Bay. So far, the temperature has been below 59 degrees more than above. We had good spawns in the last few days, but only in key places.

Water temperature at the mouth of Delaware Bay.

Water temperature at the mouth of Delaware Bay.

A key place for horseshoe crab spawn happens to be the mouths of small creeks. The New Jersey side of Delaware Bay is blessed with many small intertidal creeks, most draining only marsh or small inland watersheds. Some of these creeks have names, Goshen Creek, West Creek, Nantuxent Creek, but many do not. Almost all have shoals at their mouth with the bay because bay currents, tidal flow and wind driven waves act against each other to settle sand coming from adjacent beaches or from inside the creek drainage. Much of the sand lost from our restored beaches settles into these shoals. For horseshoe crabs, these shoals are sweet places.

A sandy shoal at the mouth of the nameless creek between Reeds and Cooks Beach. At the time of this picture, over 3,000 knots and 1,000 ruddy turnstones were using the shoal and the inner sandy beach behind the shoal. Photo by Stephanie Feigin.

A sandy shoal at the mouth of the nameless creek between Reeds and Cooks Beach. At the time of this picture, over 3,000 knots and 1,000 ruddy turnstones were using the shoal and the inner sandy beach behind the shoal. Photo by Stephanie Feigin.

Red Knots in flight on Cooks Shoal. Photo by Stephanie Feigin.

Red Knots in flight on Cooks Shoal. Photo by Stephanie Feigin.

Red Knots on Cooks Shoal. Photo by Stephanie Feigin.

Red Knots on Cooks Shoal. Photo by Stephanie Feigin.

Red Knots on Cooks Shoal. Photo by Stephanie Feigin.

Red Knots on Cooks Shoal. Photo by Stephanie Feigin.

Usually, the shoals lie just under the high tide line and are composed of large grain sand, the optimal conditions for a good crab spawn. However, the most important characteristic and key to this unusually cold May, is the warming water flowing out from the marsh drainages. On a flooding tide, colder warmer flows into the vast marshes of the Delaware Bay. This warms the water. On an ebbing tide, it flows out the creek and over the shoals, making them slightly warmer and more conducive to inducing crabs to spawn. Even on these cold days, they literally climb over themselves to breed on the shoals. The shoals also protect the inner mouths of the creeks thus making the sandy shores at the mouth of the creek a crab spawning heaven.

Breeding horseshoe crabs. Photo by Jan van der Kam.

Breeding horseshoe crabs. Photo by Jan van der Kam.

However, as it seems usual with this blog, there is a growing concern. Right now, most of the red knot population on the bay is feeding on these shoals along with thousands of other species, but only half have arrived from southern wintering areas. We now have about 12,000 red knots on the bay and in a day or two we should find another 12,000 falling from the sky. Will there be enough eggs? Will the water temperature finally reach normal levels? These are the important question for the next few days.

 

Learn More:

 

Dr. Larry Niles has led efforts to protect red knots and horseshoe crabs for over 30 years.

Cold Water Stops Horseshoe Crab Spawning along Delaware Bay

Saturday, May 21st, 2016
One of a Series of Updates on the 20th Year of the Delaware Bay Shorebird Project

By: Dr. Larry Niles, LJ Niles Associates LLC

Shorebirds and no horseshoe crabs along the Bay.

Shorebirds and no horseshoe crabs along the Bay.

It’s well known that the Delaware Bay shorebird stopover depends on horseshoe crabs, but few know that Delaware Bay is a near perfect horseshoe crab habitat.

 

There are many places on the eastern seaboard where horseshoe crabs breed. Most are too small to provide sustenance for energy-starved shorebirds. Places like Cape Romain Refuge in South Carolina have enough horseshoe crabs so that one breeding female unearths eggs of another and thus lays out a tidy meal for shorebirds. But the areas are small and at this time unimportant to the population of shorebirds. Most of the others are too small to have eggs reach the surface. Its only in Delaware Bay where crab numbers reach into the millions and spawn in such great numbers that they spread like a carpet over nearly all beaches from Gandy’s Beach to Villas, approximately 20 miles of spawning habitat. The number of eggs and ultimately hatched young reach staggering numbers.

Horseshoe crabs breeding at night.

Horseshoe crabs breeding at night.

The huge population of horseshoe crabs on the bay is no accident. The bay almost seems built to suit the crabs. Crabs need beaches with large and deep sand flats, allowing just enough water to sufficiently oxygenate the eggs without drowning them.  They need the sea floor to gently rise into breeding beaches, allowing easy access. While breeding, crabs have to eat small bivalves, which they find in abundance in the bay’s extensive intertidal and subtidal flats.

Horseshoe crab eggs.

Horseshoe crab eggs.

The most important aspect of the bay is its quickly warming waters in the spring. On Delaware Bay, horseshoe crabs don’t breed until waters reach 59 degrees. You won’t see this temperature on the Atlantic Coast until June. Not so on Delaware Bay!  Although the bay has deeper water, mostly in sloughs that snake under the surface out to its mouth at Cape May, most of the water is relatively shallow  usually less than 18 feet. That may sound deep, but keep in mind the Chesapeake has 100 feet water for most of its length and deeper water throughout. The shallow water of Delaware Bay allows it to heat up soon after the air temperature rises.

 

Unfortunately, it also cools down quickly and because of this the crab spawn has stopped. The bay’s water temperature went up dramatically in late March and April, so much so that we worried it might reach the critical 59 degree threshold in April long before the birds arrived in May. But then the warm weather stopped and the bay temperature dipped than rose, several times in fact. By early May, it had gotten just above the threshold, heating up to about 61 degrees at the Cape Henlopen marine buoy. We hoped for the best. Crabs started to breed in good numbers on a few beaches, like Reeds Beach, but were thin elsewhere. We had about 20,000 shorebird relying on the spawn and the eggs that were brought to the surface.

chart-13

Than the bay cooled down again. A nasty western wind and cold front enveloped our area over the weekend and the cool weather followed. By Monday, the temperature went down again and the crab spawn stopped. This is bad.

 

When the spawn stopped the birds hovered up the remaining eggs in a few days. Then they started wandering to find eggs in odd places, under houses, along bulkheads. Some even went to areas like the oyster aquaculture racks to find eggs to the delight of the people trying to expand aquaculture. But what they saw was desperation.

Herring gull hunting red knot, Cooks Beach, New Jersey. Photo by Jack Mace.

Herring gull hunting red knot, Cooks Beach, New Jersey. Photo by Jack Mace.

Worse the Black Back and Herring Gull that feed on eggs and overturned crabs couldn’t find eggs and started eating shorebirds. By the end of Thursday (May 19) we found 8 dead red knots. These gulls can swallow small sanderling and semipalmated sandpipers like gum drops, so we really don’t know how many shorebirds died.

Herring gull hunting red knot, Cooks Beach, New Jersey. Photo by Jack Mace.

Herring gull hunting red knot, Cooks Beach, New Jersey. Photo by Jack Mace.

Relief might be in sight though. Thursday, Friday and today will be warmer. The bay’s temperature is back up over 60 degrees. Thursday night we had a fairly good spawn. Hopefully we will be back in business soon.

 

Learn More:

 

Dr. Larry Niles has led efforts to protect red knots and horseshoe crabs for over 30 years.

Early, Good News from the Delaware Bay Shorebird Project Team

Wednesday, May 18th, 2016
A Series of Updates on Year 20 of the Delaware Bay Shorebird Project

By: Dr. Larry Niles, LJ Niles Associates LLC

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, which is always a relief at this early stage in the season. Ruddy turnstones returned in better-than-average condition, weighing in at 5 grams higher than normal arrival weights.

wieghts ruddy turnstones

P1020719 C duncan rutu banding

Team banding ruddy turnstones on Reeds Beach.

The condition on arrival is an important focus of the project. 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.

LogDbY7Htrack

Delaware Bay, New Jersey, USA

Delaware Bay, New Jersey, USA

Follow TVV’S path from Delaware Bay to its Arctic breeding area, then down to its Chilean wintering area, then 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, 5,000 miles away. Most birds will leave near nightfall, when the weather is settled and usually when there tends to be 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, others get blown off course and must struggle to return. This is the reason for the varying weights on arrival.

redknots

Red knot photo by Al Janerich.

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 on Delaware Bay beaches. At first, the birds poured into the bay.  Last Thursday May 10th, we had about 1,000 knots on the New Jersey side of the bay. By Saturday, the number has grown to 8,000 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 New Jersey bayshore. 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.

IMG_1442 (1)

Early morning on Pierce’s Point in a 30 knot wind from the west, blowing directly on shore and stopping all horseshoe crab breeding.

In our next post, learn how the winds affected the birds over the last few days.

 

Learn More:

 

Dr. Larry Niles has led efforts to protect red knots and horseshoe crabs for over 30 years.

International Migratory Bird Day Series: American Kestrel

Friday, May 13th, 2016
CWF is celebrating International Migratory Bird Day all Week Long

by Lindsay McNamara, Communications Manager

CWF’s blog on the American kestrel is the fifth in a series of five to be posted this week in celebration of International Migratory Bird Day (IMBD). IMBD 2016 is Saturday, May 14. This #birdyear, we are honoring 100 years of the Migratory Bird Treaty. This landmark treat has protected nearly all migratory bird species in the U.S. and Canada for the last century.

American Kestrel photo by Robert Lin.

American Kestrel photo by Robert Lin.

In New Jersey, catching a glimpse of an American kestrel is a rare treat! These beautiful, colorful birds of prey are about the size of a mourning dove — they are the smallest falcon in North America. Kestrels are one of two falcon species that nest in New Jersey.

 

American kestrels are opportunistic hunters, feeding on a number of different animals like grasshoppers, lizards, mice, snakes and small birds. Unlike peregrine falcons, kestrels don’t use speed to kill their prey. They perch to see their target and then use a stationary, hovering flight that allows them to dive down short distances to capture their prey. The eyespots of a kestrel make it appear to be “looking” up at its aerial predators, like Cooper’s hawks, causing the predators to move on to find a less “alert-looking” target. The eyespots give kestrels the opportunity to focus on hunting for prey beneath them.

 

Kestrels also hide surplus prey in grass clumps, tree roots, bushes, fence posts, tree limbs, and cavities, to save the food for lean times or to hide it from potential thieves!

 

Kestrels utilize these hunting tactics in open, grassy habitats — especially ones with cavities for nesting and perches for hunting. Kestrels can be seen hovering in grasslands, pastures and parklands or perched along the road on telephone lines.

 

KestrelRangeKestrels can be found in both North and South America, from Alaska and Canada in the north to Argentina in the south. During winter in North America, they will migrate southward from the northernmost portion of their range. They live year-round within New Jersey.

 

Although the American kestrel is widespread, meaning they live year round throughout much of the United States, the northeastern kestrel population is declining. Today, the kestrel is listed as a threatened species in New Jersey.

 

The decline of kestrels in New Jersey is likely due to destruction of grasslands from development. Nesting cavities are also being lost. As humans clean up fields, we remove trees with nest cavities that kestrels use. Kestrels are secondary cavity nesters. They don’t make their own cavity but use existing natural or man-made cavities.

 

Since kestrels nest in buildings and other man-made structures, nest box programs are an effective way to help grow the number of kestrels in areas where nest sites are limited.

 

Conserve Wildlife Foundation of New Jersey, in partnership with the Endangered and Nongame Species Program implemented a nest box installation and monitoring program in 2006. Nest boxes have been placed in areas of habitat determined to be suitable for the birds of prey. The boxes are monitored by biologists during the breeding season. Because kestrels reuse nest sites, particularly if they have successfully raised young, we focus on boxes that have been successful at least once since 2006.

 

The nest box program in New Jersey appears to be successful; we are adding to the population. Since 2006, we have banded over 300 fledglings. You can help too! Next time you see an American kestrel in the Garden State, be sure to submit a Rare Species Sighting form.

 

Learn More:

 

Lindsay McNamara is the Communications Manager for Conserve Wildlife Foundation of New Jersey.

International Migratory Bird Series: Great Blue Heron

Thursday, May 12th, 2016
CWF is celebrating International Migratory Bird Day all Week Long

by Lindsay McNamara, Communications Manager
CWF’s blog on the great blue heron is the fourth in a series of five to be posted this week in celebration of International Migratory Bird Day (IMBD). IMBD 2016 is Saturday, May 14. This #birdyear, we are honoring 100 years of the Migratory Bird Treaty. This landmark treat has protected nearly all migratory bird species in the U.S. and Canada for the last century.

Great blue heron by Howie Williams (8)

Great blue heron photo by Howie Williams.

Have you seen a great blue heron wading in the marshes of the Garden State? While they are commonly seen along shorelines, river banks, and the edges of marshes, estuaries, and ponds, the breeding population of these wading birds is actually listed as a Species of Special Concern in New Jersey.

 

The term ‘Species of Special Concern’ applies to wildlife species that warrant special attention because of some evidence of decline, inherent vulnerability to environmental deterioration, or habitat modification that would result in their becoming a Threatened species.

 

Great blue heron photo by Howie Williams.

Great blue heron photo by Howie Williams.

Due to its wide distribution, varied diet, and flexibility in nesting near both freshwater and saltwater environments, the great blue heron’s population in North America is stable. However, wetland destruction in New Jersey has caused a decrease in heron populations from their historic numbers. Since the 1950s, habitat loss has occurred at an alarming rate in New Jersey, destroying wetlands critical to breeding herons.

 

Protecting our wetland habitats from disturbance and development will help protect the great blue heron, the largest wading bird in North America. Great blue herons are 46 inches long and have a wingspan of 72 inches. Despite their large size, great blue herons only weigh 5 to 6 pounds, in part because of their hollow bones — a feature all birds share.

 
Great blue herons can hunt during the day and night, thanks to a high percentage of rod-type photoreceptors in their eyes that improve night vision. They eat nearly anything within striking distance, including fish, amphibians, reptiles, small mammals, insects, and other birds. Herons nest in colonies or “rookeries” in tall trees near bodies of water.

 

The oldest great blue heron on record was found in Texas when it was at least 24 years, 6 months old!

 

RangeMapThe great blue heron occurs throughout most of North America, from Alaska and eastern Canada in the north to the northern portion of South America in the south. Northern populations of great blue herons east of the Rockies are migratory.

 

They withdraw from the northernmost portion of their range during the winter, some traveling to the Caribbean, Central America or northern South America. This species breeds throughout New Jersey. They generally do not occur within the northwestern corner of the Garden State during winter. Great blue herons migrate singularly or in small flocks, mainly in daytime.

 

We still have much to learn about the biology and population status of great blue herons in New Jersey. Research needs to be conducted to find additional breeding sites, check existing nesting areas, and determine whether the population might be decreasing or increasing. You can help! Next time you see a great blue heron in the Garden State, be sure to submit a Rare Species Sighting form.

 

Learn More:

 

Lindsay McNamara is the Communications Manager for Conserve Wildlife Foundation of New Jersey.

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