Earlier Springs Due to Climate Change?

One of the issues discussed in the paper I reviewed for yesterday's post was the possibility that climate change could interfere with the migration ecology of Red Knots. Climate change theory predicts that a warmer climate will bring more frequent and intense storms to our area. Since severe weather delays the timing of horseshoe crab spawning, future Red Knots could face more frequent springs when they arrive before most horseshoe crabs have spawned. Such a disruption could have a severe impact on their survival.

Disruptions due to a changing climate may harm plants as well as animals. A recent study found that plants are blooming earlier than they used to.

A University of Alberta study shows that climate change over the past 70 years has pushed some of the province's native wildflowers and trees into earlier blooming times, making them more vulnerable to damaging frosts, and ultimately, threatening reproduction.

U of A PhD candidate Elisabeth Beaubien and her supervisor, professor Andreas Hamann of the Department of Renewable Resources, studied the life cycle of central Alberta spring blooms, spanning 1936 to 2006, evaluating climate trends and the corresponding changes in bloom times for seven plant species.

Using thermal time models, the researchers found that the bloom dates for early spring species such as prairie crocuses and aspen trees had advanced by two weeks over the stretch of seven decades, with later-blooming species such as saskatoon and chokecherry bushes being pushed ahead by up to six days. The average winter monthly temperature increased considerably over 70 years, with the greatest change noted in February, which warmed by 5.3 degrees Celsius.

Changes in the time of blooming will no doubt affect the plants' relationships with the insects that pollinate them or other animals that use them for food.

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.

Underwing Under Water

This moth was floating in a tub of water outside after the recent rains. It was still alive and energetic enough to stand up and walk around once it had dried sufficiently. Unfortunately its left wings must have been damaged while it was struggling in the water, or perhaps they just dried at an odd angle.

It appears to be an underwing-type moth, but that is where it gets tricky. True underwings are in genus Catocala, but there are several genera that feature similarly bold hindwing patterns, paired with a cryptic forewing. The forewings on this moth are very worn; the involuntary bath must soaked a lot of them off, especially near the bases of the wings. This makes the forewing pattern very difficult to interpret.

The hindwing pattern seems to fit Catocala sordida, the Sordid Underwing, or something like it. In particular, it has two black bands crossing an orange ground color, with the inner band making a complete  loop and the outer band having a white spot at the apex and a gap near the inner margin. However, the hindwing also has a black costa (leading edge), which seems unusual for a Catocala. So that leaves me somewhat uncertain of the moth's true identity.

Pigeons Can Remember Faces Too

In my last Loose Feathers, I linked to an article about research showing that wild crows can recognize people by their faces, particularly when the people in question might pose a threat. In that case, some scientists doing a banding study in Seattle noticed that crows started mobbing them whenever they returned to a banding site where crows had been caught and banded. So they ran some experiments, which you can read about at the link, and determined that the crows were most likely responding to their faces rather than their garments or other accessories. Not only that, but crows could remember those faces for years afterwards, and the information that those faces were dangerous spread through the crows' social networks.

Another recent study found that feral pigeons have a similar ability to recognize faces.

Previous research in this arena had only focused on the perception abilities of pigeons that were trained in a lab environment, but the new study was conducted on untrained feral pigeons. At a park in Paris, two researchers of similar build and skin color, but wearing different-colored lab coats, fed a group of pigeons.

One researcher ignored the pigeons after feeding them, allowing them to eat the food, while the other was hostile and chased them away. This was followed by a second session when neither researcher chased away the pigeons.

The experiment was repeated several times, with the pigeons continuously recognizing the individuals and avoiding the researcher who had first chased them away even when the participant no longer did so. Swapping lab coats during the experiments did not confuse the pigeons, and they continued to stay away from the researcher who had been initially hostile.

"It is very likely that the pigeons recognized the researchers by their faces, since the individuals were both female and of a similar age, build and skin color," study researcher Dalila Bovet of the University of Paris Ouest Nanterre La Défense said in a statement.

"Interestingly, the pigeons, without training, spontaneously used the most relevant characteristics of the individuals (probably facial traits), instead of the lab coats that covered 90 percent of the body," Bovet added.

It would be interesting to see whether pigeons have a long-term memory, as crows do, and if information about the threat is spread socially.

Butterflies and Dragonflies at Scherman Hoffman

Yesterday I was at Scherman Hoffman Wildlife Sanctuary, a nature refuge run by New Jersey Audubon in Bernardsville, to see what sorts of wildlife would be active there in midsummer. Most birds are well into their breeding season, but many were still singing. I was delighted to hear several singing Veeries; as I have noted before on this blog, the Veery's song is one of my favorites. Other singers included Wood Thrush, Indigo Bunting, House Wren, Chipping Sparrow, Ovenbird, and Common Yellowthroat. Some birds were clearly tending young already. I saw one House Wren perched in the entrance of a nest box (with another singing nearby) and a Black-capped Chickadee carrying a caterpillar, presumably to its nest site.

Despite the bird activity, I was more drawn to the insect activity yesterday. I had hoped that I might find a Harvester, an uncommon butterfly in New Jersey that is known to occur regularly at that preserve's beech groves, but I did not spot any. In addition to being a very attractive butterfly, it is North America's only predatory butterfly species: Harvester caterpillars prey on Woolly Aphids. Instead, I was treated to an array of other invertebrates. Great Spangled Fritillaries, like the one above, were active in great numbers; at one point I had six in one binocular field.

After seeing my life Delaware Skipper last week, I got to see another one this week.

I am pretty sure that this Northern Broken-Dash was a lifer; my butterfly records from past years are not thorough enough to be certain, but I have no recollection of seeing one before. This small, dark skipper could easily have passed unnoticed.

Dragonflies were active too, particularly in the area around a vernal pool close to the road. The dragonfly above is a Blue Dasher, one of the most common dragonflies in the area. This individual confused me at first since it was not holding its wings in the characteristic Blue Dasher posture.

Finally, this Spangled Skimmer was a dragonfly lifer for me. There were several of them perched among the cattails, some more worn than others. Above is a fresher individual, and below is a more worn one.

Summer Flowers

With the turn of the seasons from spring to summer, there has also been a shift in the flowers in bloom. Here are a few early summer flowers that started blooming within the past two weeks.

Monarda didyma, also known as bee balm or Oswego tea.

Another species of Monarda, Monarda fistulosa, usually called wild bergamot.

Woodland sunflowers, Helianthus divaricatus, are also coming into bloom.

Finally, fleabane (Erigeron sp.) is blooming profusely anywhere it is allowed to grow.

Loose Feathers #297

Lewis's Woodpecker / Photo by Dave Menke (USFWS)

 Birds and birding news

• Scientists in New Zealand are rehabilitating the penguin that got lost and arrived there; they plan to release the penguin into the Pacific near the northern border of the species's known range.
• A new recovery plan for the Northern Spotted Owl will propose additional old growth forest conservation within the owl's range. The plan will also experiment with removing some Barred Owls to see if reduced competition makes a difference.
• By studying fossil birds with X-rays, scientists found that two ancient birds, Confuciusornis sanctus and Gansus yumenensis, carried eumelanin in some of their feathers. Eumelanin is a pigment that produces copper and dark brown coloration.
• Crows can remember the faces of people that wrong them several years after the incident, and crows can spread the word about them to other crows. This is the conclusion of a banding study, in which scientists who trapped and banded crows still get mobbed by those crows and their flockmates five years after the original banding.
• Conservationists are concerned that the Red-cockaded Woodpecker population will outgrow their limited habitat.
• The American Bird Conservancy wants visitors to beaches during Fourth of July weekend to be careful not to disturb beach nesting birds. Unfortunately, not all beachgoers heed such warnings, as some nest sites are occasionally vandalized.
• Scientists wonder if climate change will disrupt the timing of horseshoe crab spawning and Red Knot migration around Delaware Bay.
• Hoffman Island, off Staten Island in New York Harbor, was formerly a quarantine site for immigrants but is now home to nesting colonies of Double-crested Cormorants and other waterbirds.
• A federal judge gave three federal agencies six months to improve the management of four national forests (Angeles, Cleveland, Los Padres and San Bernardino) to benefit 40 endangered species, including the California Condor and California Gnatcatcher.
• Kittiwakes' migratory movements are dependent in part on ice cover, so changes in climate are likely to affect their migration patterns.
• Here is a photo gallery of the Dismal Swamp in central New Jersey.
• A man in South Carolina killed a gull with a bat for flying over his food.
• Three men were arrested for illegally trafficking in Bald Eagle feathers. The feather trade violated the Bald and Golden Eagle Protection Act, the Migratory Bird Treaty Act, and the Lacey Act.
• Flooding in the Midwest no doubt wiped out a lot of this year's nests, but it is too soon to tell what the long term effects will be. It was not all bad news for birds, as the flooding allowed Least Terns to take over a portion of the Birds Point New Madrid Floodway for nesting.

Nature blogging

• Diary of a Mad Natural Historian: Fuertes and Abyssinia
• BirdWatching Field of View: How safe is mist netting? First large-scale study into bird-capture technique finds little risk to birds
• Not Exactly Rocket Science: Parasitising Grandma – why alien eggs can be a sign of helpful families
• Coffee & Conservation: Climate change impacts on coffee nations
• Sibley Guides: Powder down and the Black-crowned Night-Heron
• Audubon Guides: Amazing Feets
• The Skeptical Moth: The incredibly loud world of bug sex
• View from the Cape: Baby Boom
• Fotoportmann: Rocky Point Marsh: Jamaica Bay, NYC
• The Freiday Bird Blog: Salt Marsh Morning
• Tetrapod Zoology: Hoopoes and woodhoopoes

Environment and biodiversity

• New York reached an agreement with environmental groups on a plan to complete the cleanup of Jamaica Bay. The city will improve four sewage plants to reduce nitrogen pollution by 2020, and it will create a fund to restore salt marsh habitat around the bay. The city also hopes to have the bay designated as a "no discharge zone," so that boaters will not be allowed to discharge their sewage tanks into the bay.
• Temperatures across the United States averaged 0.5°F warmer during the 30 years from 1981-2010 than from 1971-2000. The climate of the 2000s is 1.5°F than the climate of the 1970s. Meanwhile, May 2011 was above average globally, but in the U.S., it was cooler than average.
• East Africa is experiencing its worst drought since 1950-1951.
• The Wallow Fire in Arizona probably killed some of the state's Mexican Spotted Owls as it burned through 73 protected nesting areas, but its Mexican Gray Wolf packs escaped. Officials will need to protect endangered Apache and Gila Trout from future runoff related to the fire. Meanwhile, Santa Fe National Forest and other parkland are closed due to the Las Conchas fire.
• Over 1,060 new species were discovered on the island of New Guinea over the past 10 years. The discoveries included 218 plants, 580 invertebrates, 134 amphibians, 2 birds, 71 fish, 43 reptiles and 12 mammals.
• Wildlife are managing to survive in Afghanistan despite years of warfare. Here is a gallery of Here is a gallery of some of the country's animals.
• The development of disease-resistant oysters may change Chesapeake Bay restoration strategies.