Archive for July, 2013

Jul 31 2013

Mysterious Disappearance

House sparrow (photo by David Lofink via Wikimedia Commons)

If you live in North America this fact is amazing:  House sparrows are an endangered species in Britain.

I learned this when I read John Metcalfe’s article called Making Cities More Bird Friendly With Nesting Bricks.  In it he describes a new brick specially designed by Aaron Dunkerton and manufactured in England to provide habitat for nesting house sparrows.  Before mortar is applied it looks like this.  (Click on the bricks to read about them.)

Bird brick by Aaron Dunkerton (image from Aaron Dunkerton's website)

House sparrows are the most widely distributed wild bird on earth.  Why are they so endangered in the U.K. that people invent ways to help them?  Here’s what I found out.

Since 1977 house sparrows have declined by 71% in Britain.  In some locations they are nearly extirpated.  London’s Kensington Park had 2,603 house sparrows in 1925.  By 2000 there were only 18.

Despite many studies a single cause has not been found and no other urban/suburban bird has experienced a similar decline.

In 2005 Kate E. Vincent published a house sparrow population study.  In 2009 Lorna Margaret Shaw investigated the role of neighborhood socio-economic status in house sparrow abundance.  These studies found:

  • The greatest house sparrow declines occurred where nestlings starved within a week of hatching or had low fledging weight, both due to lack of insect prey.  The best success occurred where they ate plenty of aphids or spiders.  (Aphids come up again!)
  • Because house sparrows nest in holes in buildings, they did well in neighborhoods built before 1919, in neighborhoods where soffitt and fascia were made of wood, and in distressed neighborhoods where the buildings needed repairs.  They avoided neighborhoods built after 1985 because of new construction standards and lack of deterioration.  That’s why Aaron Dunkerton invented the bird brick for new homes.
  • House sparrows did poorly in tidy neighborhoods with lots of paving.  Over the years Britons have paved their front yards and removed trees and shrubs so they can park their cars.  This has reduced house sparrow habitat.
  • All habitat was not equal.  House sparrows preferred deciduous plants and the insects associated with them.
  • House sparrows did not use ornamentals or evergreens.  This lead to a headline that Leylandii hedges were to blame for the house sparrow decline.  (A fascinating topic…more on that tomorrow.)

With so many factors in play there’s no simple answer to the house sparrow’s mysterious disappearance.  In the meantime they continue to decline and Britons miss them terribly.

If it would work I’d package some of ours and send them to England.  We have a house sparrow surplus right now.

 

(photo of a house sparrow in California from Wikimedia Commons. Nesting bricks by Aaron Dunkerton.  Click on the images to see their originals.)

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Jul 30 2013

Oak Wilt Strikes Again

Published by under Schenley Park,Trees

Oak wilt in Schenley Park, 5 July 2013 (photo by Kate St. John)

I love trees so much that I jump at the chance to learn more about them.

Back in February 2011 I learned about the threats facing 60% of our city park trees when the Pittsburgh Parks Conservancy presented a public event called Preserving Pittsburgh’s Trees: Action and Recovery.   I was already familiar with emerald ash borer since I first saw it in Schenley in May 2010 but I learned about something I’d never seen before: oak wilt.

While Schenley Park had been coping with the death of all its ash trees, the other three big parks — Frick, Highland and Riverview — had experienced oak wilt as well.

Oak wilt is caused by a fungus that doesn’t spread easily but can kill a tree in 30 days.  The fungus travels in the oak’s vascular system and when the tree detects it it blocks those vessels.  The blockage kills the tree. It’s the arboreal equivalent of a stroke.  Watch the 13 minute video here to see how this happens.

After the conference I began to watch Schenley’s oaks with new interest.  Two years passed.  Early this month I could tell something wasn’t right at Prospect Circle.  I emailed this and other photos to Phil Gruszka, Director of Park Management and Maintenance at the Pittsburgh Parks Conservancy, and he confirmed that oak wilt had struck again.  He also started the ball rolling to eradicate it.

Fortunately the fungus spreads slowly and that’s the key to stopping it.  It’s either carried into an open wound by sap-eating beetles (this is harder than you think) or it travels from oak to oak via root grafts.  Amazingly, the roots of adjacent oaks graft to each other when they touch underground.  In a pure oak stand they become one huge vascular system.

There is no cure but future deaths can be prevented by cutting down the affected trees, trenching the perimeter to prevent uninfected roots from entering the danger zone, and medically treating the oaks just outside the perimeter.

In the not too distant future a large patch of dead and dying oaks will be chopped down at Prospect Circle.  This will look ugly at first but will save all the other beautiful oaks along the road and hillside.

For more information about oak wilt, read these Pittsburgh Parks Conservancy blogs about the episode in our parks in 2010:

 

(photo of the oak wilt trees in Schenley Park, July 2013, by Kate St. John)

 

p.s. Learn more about the trees in our city parks at this link on the Pittsburgh Parks Conservancy website.

UPDATE on 18 October 2013 from the Pittsburgh Parks Conservancy –> click here.

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Jul 29 2013

Will They Kill 3,600 Barred Owls?

Barred Owl (photo by Chuck Tague)

A troubling plan slipped under the radar of Easterners who care about barred owls and native birds.

In the Pacific Northwest, northern spotted owls have been listed as threatened since 1990 under the Endangered Species Act.  The number one cause for their decline is the logging of old-growth forest.  The logging stopped in the national forests in 1991 but the spotted owl continues to decline, especially in smaller forest tracts.

Barred owls are distant relatives of the northern spotted owl.  They formerly lived only east of the Great Plains but for 100 years they have slowly spread north and west and now inhabit the Pacific Northwest as well.

In recent years biologists studying spotted owls noticed the spotteds declined in zones where barreds increased, so U.S. Fish and Wildlife Service has proposed killing barred owls as an experiment to see if this helps the northern spotted owl.

The proposal, published in March 2012 as a Draft Environmental Impact Statement, included a public comment period.  We may not have noticed the proposal but westerners saw and commented.

The comments were overwhelmingly negative from “Don’t do it!” to “This is stupid!” to an excellent letter by biologist Elizabeth Ellis who has studied northern spotted owl populations and pointed out the flaws in the proposal including the lack of barred owl population studies (it is threatened in parts of its range!), unknown human contribution — if any — to the barred owl’s range movement, the fact that the proposal tracts where barred owls have gained a foothold are known to be too small to adequately protect the northern spotted owl, and the wisdom of using limited management funds to kill an unstudied species.

If I’d had a chance to comment I would have said…  (stepping up on my soapbox)…

Humans directly caused the disappearance of 90% of the Pacific Northwest old growth forest. When species are going extinct because of our actions we have a choice:  Do we cut down the last 10% of the forest or stop logging?  We can control the things that humans do, however…

We cannot control the rest of Nature.  Humans did not actively introduce the barred owl.  We don’t fully know why it arrived.  It is hubris to think we can control what’s happening by killing it.

The barred owl is so closely related to the northern spotted owl that the two can interbreed. The barred owl may be adding strong genes that the spotted owls need to survive.  Interbreeding is anathema to species purists but it’s how nature works.  Would we cull blue-winged warblers because they interbreed with and seem to out-compete the less abundant golden-winged warbler?  Culling native birds to protect a favorite species is a dangerous precedent.

The Pacific Northwest is not an isolated island so barred owls will continue to naturally arrive in the northern spotted owl’s territory.  If the proposed experiment works the culling will have to continue as long as humans have the stomach and the money to do it.

I could go on and on…

At this point it is up to U.S. Fish and Wildlife Service to decide whether to go forward with their plan.  I hope they drop it like a hot potato!

(stepping down from my soapbox…)

Thanks for listening.

Click here for information from the U.S. Fish and Wildlife website on their plan to kill 3,600 barred owls in the Pacific Northwest.

(barred owl in Florida, photo by Chuck Tague)

10 responses so far

Jul 28 2013

Predatory Ladies

Published by under Insects, Fish, Frogs

Ladybugs hunting aphids (photo by Kate St. John)

Ever since I wrote about aphids a few weeks ago, I stop to look for their predators.

Last weekend I saw ladybugs in action.  They’re such great predators of aphids that Asian lady beetles were imported in the 1970′s as a biological pest control.

I watched them make a dent in the aphid population on joe pyeweed.  One lady beetle absolutely ran from stem to stem checking for aphids.  She abandoned flower heads with too few aphids and even turned back when she found a stem completely coated in aphids (too many?).  I saw her chase an aphid, then finally settle down to work on this flower head.

This must have been a good site.  How many ladybugs can you count?  (More than appear at first.)

Notice that these ladies are spotless.  They’re the Asian species.  Our native ladybugs always have spots and are in decline because the Asian lady beetles carry a fungal parasite that kills the natives.

The bad news is that Asian ladybugs are overtaking the natives.  The good news is that we have ladybugs and they’re eating the pests.

Good job, ladies!

(photo by Kate St. John)

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Jul 27 2013

Tall Bellflower in Bloom

Published by under Plants

fThree stems of Tall Bellflower joined by a vine (photo by Kate St. John)

I almost forgot the name of this plant when I found it blooming last weekend.

Despite the fact that the flower is not bell-shaped, this plant is called tall bellflower (Campanulastrum americanum).  The flowers are a pretty shade of cornflower blue and have an ornate pistil arrangement that looks like a stripped down version of the purple passion flower, also known as maypops.

Here are side-by-side close-ups of maypops and tall bellflower so you can see what I mean.

Compare purple passion flower to tall bellflower (photo of maypops from Wikimedia Commons, photo of bellflower by Kate St. John)

 

The stems in the first photo are in an unusual arrangement.  They’re bunched because a vine wrapped the three together.  Click here for a more typical view.

 

(tall bellflower photos by Kate St. John. Maypops from this page at Wikimedia Commons)

 

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Jul 26 2013

The Sleeping One

Published by under Tenth Page

Common Poorwill (photo by Dominic Sherony via Wikimedia Commons)

While reading about birds’ response to heat stress I came across this amazing story of a bird that appears to hibernate!

The common poorwill (Phalaenoptilus nuttallii) is the smallest North American nightjar, a member of the family Caprimulgidae that includes the common nighthawk and eastern whip-poor-will.  He lives in the arid West and, like his relatives, hunts for insects on the wing at dusk and dawn and on moonlit nights.

Flying insects are an unpredictable food source so when the weather’s bad or food supplies are low the poorwill prevents starvation by entering torpor.  He roosts, drops his body temperature to as little as 4.3oC (40oF) and reduces his oxygen intake by more than 90%.  He can do this on a daily basis if he has to and can even enter torpor while incubating eggs.

Poorwills take torpor to an extreme.  Rather than leave North America for the winter as nighthawks do, the poorwills remain in northern Mexico and the southwestern U.S. where winter can be too cold for flying insects.  They cope by entering torpor and staying there for two to three months!

To help themselves wake up they choose a location where the sun will warm them.  It needs to be a safe place because it takes seven hours for them to fully heat up.  This is probably why they are small.  The larger the animal, the longer it takes to leave torpor.

The Hopi knew this bird’s amazing trait and named him Hölchoko — “The Sleeping One.”

 

(photo from Wikimedia Commons. Click on the image to see the original.  Today’s Tenth Page is inspired by page 160 of Ornithology by Frank B. Gill.)

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Jul 25 2013

Great Golden Digger

Published by under Insects, Fish, Frogs

Great golden digger wasp on spreading dogbane (photo by Kate St. John)

I always look for birds when I’m outdoors but they just aren’t as conspicuous as the bugs are in July.

Last weekend on the Montour Trail I found a large black-and-orange wasp feeding on spreading dogbane.  It attracted my attention because it was huge and had bright orange legs and abdomen.

My search at bugguide.net identified it as a great golden digger wasp (Sphex ichneumoneus).

The name is apt.  They are huge, golden (their foreheads are gold!), and they dig a hole to create their nests.

Great golden diggers are solitary.  To make a nest a female digs a vertical hole with lateral chambers.  For each egg laid, she captures and paralyzes a katydid or grasshopper, then drags it into one of the chambers, lays an egg on it and seals the chamber.  The larva feasts on the paralyzed insect and emerges as a wasp.  Read more of this amazing story here.

I tried to get a good photo showing her orange body.  Below she flaps her wings to perch on an unstable flower.

Great golden digger wasp (photo by Kate St. John)

 

Was I afraid she’d sting me?  No.  She was too busy feeding.

Later I learned I had nothing to fear.  Though intimidating, this species is not aggressive.

 

(photos by Kate St. John)

p.s. Check the video link at “Art from Hershey, PA”s comment below to see what the digger’s nest looks like from above.

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Jul 24 2013

Has Used A Motorcyle

Aplomado falcon (photo from Shutterstock.com)

Some raptors have special techniques for finding food.  This one has used trains and motorcycles.

Aplomado falcons (Falco femoralis) are native to grassland and marshland from Mexico to South America where they eat birds, insects and small vertebrates.  Sometimes they hunt while soaring or from a perch but when hunting birds they prefer to fly fast through thickets to flush them from cover. This technique is similar to a Coopers hawk.

Mated pairs like to hunt cooperatively.  The male makes a distinctive “chip” sound to call his mate to a hunt.  Sometimes the female will even come off the nest to participate.  The male corners the prey by hovering above the thicket.  The female flies through and flushes it.

When his mate can’t come out to hunt, what’s a guy to do?  Borrow a motorcycle.

Aplomados have figured out that our large, loud vehicles scare small birds into flight.  According to Birds of North America online, one researcher reported an aplomado following a motorcycle to pick off small birds flushed from the side of the road.  Another reported a falcon flying with a train and switching sides to check out the ditches.

These falcons were extirpated from the U.S. in the 1950′s and only recently made a comeback in New Mexico and south Texas, partly on their own and partly thanks to reintroduction programs.

When I travel southwest to find an aplomado I wonder … will it help to watch for motorcycles?

 

(photo from Shutterstock.com)

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Jul 23 2013

These Are Not Pine Cones

Bagworm moth caterpillars on cedar tree (photo by Stephen Tirone)

When Steve Tirone learned the identity of these pine cone look-alikes he had his work cut out for him.

Early this month he sent me this photo (below) and asked:  “Any idea what this is? I had a few on my house last year. They are near my cedar tree.”

Bagworm moth caterpillar (photo by Steve Tirone)

I emailed Monica Miller who replied: bagworm moth caterpillar.

Bagworms adorn themselves with disguising vegetation that eventually becomes their pupating bag.  Until then they chow down on their favorite foods.

Steve looked closely at his cedar tree and discovered it was covered in caterpillars that were eating it alive.  No wonder it looked sick!  He also learned that pesticides don’t work on these bag-covered bugs.  The only way save his tree was to pull off each one by hand, as in…

[I picked them off] for 2 hours today, along with chopping out large parts of the tree.  Ugly work, ugly results, and there are still tons left. Every time I go by the tree I say “How did I miss that one, and that one?”  Easy, because they look just like pine cones!

If any remain on the tree, what will happen next?

Monica did not specify the bagworm species — there are over 1,000 of them worldwide — but I’ll tell you the story of the evergreen bagworm moth (Thyridopteryx ephemeraeformis (Haworth)) because it’s a particular pest of cedars (Thuja occidentalis also called arborvitae).

From May to August the caterpillars eat and mature through seven instars.  In August the mature caterpillars prepare to pupate by hanging their bags from host plants by a strong silken thread.  Then they turn around inside the bag to face downward.

Four weeks later, in September and early October, the males emerge.  They’re about an inch long and are easy to overlook because they’re small and black, about an inch long.  They eat nothing.

Bagworm moth (photo by Mark Dreiling, Retired, Bugwood.org)

The females never emerge.  They’re wingless, legless and have no functioning mouth parts.  They’re just a bag of eggs and pheromones waiting for a male to land on their bag and mate with them.

As soon as the females have mated they shut off their pheromones and lay 500-1,000 eggs inside the pupal sack inside the bag.  They live a couple of weeks, crawl out of the bag to die or become mummified inside.  The males are long gone, having died within a day or two of their emergence.

Over the winter the bag hangs on the tree with 500 to 1,000 potential caterpillars waiting to hatch next spring.

If you pull these bags off your cedars before April you’ll save your trees a lot trouble.

moth_bagworms_in_cedar_1860096_rsz_bugwoodTwo bagworm moths overwintering on a cedar (photo by Lacy L. Hyche, Auburn Univ, Bugwood.org)

For more information see this fact sheet from Penn State.

 

(first two photos by Stephen Tirone.  Moth photo (5462023) by Lacy L. Hyche, Auburn University via bugwood.org.  Bags photo (UGA1860096) by Mark Dreiling via bugwood.org)

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Jul 22 2013

Unexpected Consequences

Black rat snake looking for birds' nests (photo by Jarek Tuszinski via Wikimedia Commons)

The headline read: Snakes devour more mosquito-eating birds as climate change heats forests.

Oh no!

In a recently published study, University of Missouri biologist John Faaborg analyzed 20 years of nesting data in the Missouri Ozarks forest and found a direct correlation between hotter nesting seasons and nest failure.

The reason?  Snakes.

Twenty years ago the Ozark forest was cold enough that bird-eating snakes were less active and hungry but hotter years have changed that.  Among others, acadian flycatchers and indigo buntings have borne the brunt of the snakes’ new-found activity.

Faaborg’s finding is bolstered by a University of Illinois study published last January that predicts increased nighttime snake activity as an outcome of climate change.

University of Illinois researcher Patrick Weatherhead and his students studied black rat snakes in Texas, Illinois and Ontario as a proxy for hot, moderate, and cool climates.   They fitted the snakes with tiny temperature-sensitive radio transmitters which enabled them to know the snakes’ location and the ambient temperature.  Temperature is important because snakes are cold-blooded.  The researchers also placed cameras on hundreds of birds’ nests so they’d know exactly what happened and when.

The results were frightening for birds.  In Texas the days are too hot for black rat snakes so they’re mostly active at night.  Unfortunately this is very bad for nesting birds because they can’t see the snakes coming.  Not only do the snakes eat the eggs and nestlings but they often eat the female parent because she’s caught on the nest unawares.

In Ontario the nights are too cold for snakes so they’re only active during the day.  When snakes approached nests in daylight, the adults left the nests and raised alarms which attracted hawks to come eat the snakes.  Nesting birds had a better chance for success in this cooler climate.

Illinois’ moderate climate showed that black rat snakes are adaptable.  When nighttime temperatures were warm enough the snakes came out to hunt.

So climate change won’t just be hotter, stormier weather.   Its unexpected consequences are not fun at all:  More snake activity and fewer mosquito-eating birds.

Oh no!

(photo of a black rat snake from Wikimedia Commons.  Click on the image to see the original)

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