“Birds are classically among the most monogamous of all organisms,” writes Frank B. Gill in Ornithology.
Many birds mate for life. Swans and geese, parrots and eagles, albatrosses and even pigeons choose a mate once and for all. Among those species divorce is rare. That’s why a Bewick’s swan couple caused a stir when they arrived on their wintering grounds in 2009, apparently divorced and remarried. They were the only Bewick’s swans known to do it in 40 years.
Do other monogamous birds ever divorce? Is it typical behavior that we hadn’t noticed?
In 2000, Scott M. Ramsay and his team published an eight year study of black-capped chickadee social life. Using bird bands and DNA testing they discovered that young females who have low confidence in their mates initiate divorce after their first breeding season and remarry on a more permanent basis for their second year of motherhood. The team even found out why.
When black-capped chickadees pair up the males sing to maintain their territories and the females listen to determine who’s strongest. When a first-year female hears her mate fail she remains with him but mates with other males as well, producing a clutch of mixed paternity. She and her husband incubate and raise the nestlings but before the next breeding season she files for divorce and marries someone of higher social rank.
The study found that the ladies who “messed around” were the ones most likely to divorce.
Browsing through photos on Wikimedia Commons, this portrait of a falcon caught my eye. He’s one of six species of falcons found in Australia, new to me because he doesn’t occur in North America. The only falcon we all have in common is the peregrine.
The brown falcon (Falco berigora) is slightly smaller than a peregrine and has a different lifestyle. Rather than capture prey in the air he uses a perch-and-pounce method to capture small mammals, lizards and snakes, small birds, and insects. This is similar to the red-tailed hawk’s hunting technique.
Brown falcons don’t need to fly fast. Their wing beats are slow and they glide in a shallow V the way northern harriers do.
Though they share characteristics with hawks, Perth Raptor Care says they have a lot of personality. Click here for a video at Arkive.org that gives you a window on the lives of brown falcons: contending with crows, sharing with a mate, feeding the “kids.”
I love their brown pantaloons.
(photo from Wikimedia Commons. Click on the image to see the original)
Here’s a flower so common you might think it’s a weed.
Fleabane is native to North America and very common in western Pennsylvania. It grows so easily that you’ll find it along roadsides.
Pictured here is daisy fleabane (Erigeron annuus) in Schenley Park. Its white or pink-tinged flowers are 0.5 to 0.75 inches wide and its leaves do not clasp the stem. Common or Philadelphia fleabane (Erigeron philadelphicus) has slightly larger, pinker flowers and its leaves *do* clasp the stem. To remember this think “Common = Clasp.”
Fleabane flowers respond to light. The white rays open and close at sunrise and sunset. Before they bloom they bow their heads. In the morning fleabane pulls up its flower heads and opens its white rays. This seems like a lot of exercise for a small flower but I imagine it’s meant to prevent nighttime pollination.
Fleabane got its name from the belief that the dried plant kills fleas. Bane comes from an Anglo-Saxon word meaning murderer or destroyer and is often used in plant names. For instance, “baneberry” means death-berry; it’s poisonous.
If wanted to kill fleas I could dry some fleabane. Thankfully I’ve never had occasion to need it.
African starlings evolve color faster than any other bird — 10 times faster than their ancestors and modern relatives according to a new study from the University of Akron.
Like other Sturnidae these birds had iridescent qualities, but after they made it to sub-Saharan Africa 17 million years ago their colors went wild. The cells that give their feathers iridescence are called melanosomes. Instead of the usual simple rod-like forms, glossy starlings (Lamprotornis) developed hollow rods, solid flattened rods, and hollow flattened rods. Though these divergent melanosomes are sometimes found in other birds, glossy starlings can have all the variations in one species. This produced an explosion of new colors.
At the University of Akron Rafael Maia studied microscopic feather structures and used spectral color analysis and evolutionary modelling to figure out how these starlings evolved four types of melanosomes and 19+ species. It happened very fast.
Their social structure helped. For glossy starlings, color confers high rank in both sexes so the most colorful birds are the most successful breeders. Intense social pressure selected for better and better colors.
If you’re near Schenley Park or passing through as I do, stop by the Farmers’ Market on the lawn at Phipps Conservatory, Wednesdays at 2:30pm to 6:30pm, for fresh organic and naturally grown food. Click here for more information.
As soon as the woodland sunflowers started to bloom in Schenley Park their stems became coated with tiny red bugs. Last weekend I took the camera to the Upper Trail to see what the red was all about.
It didn’t take long to figure out these are red aphids. Nose down, probiscus inserted, they sucked the sunflower juices. They only ate from the Helianthus species, never from other plants nearby.
Among the hundreds of aphids I found a few with wings, the dispersal generation that can fly to new hosts. In the photo above there’s a winged adult hiding behind the flower bud.
Most fascinating was their wide range of sizes. From incredibly tiny to full grown adults there were many generations on one plant. I saw no larvae, just fully formed bugs, because of their incredible reproductive strategy.
In the summer all aphids are female! They reproduce asexually and give birth to live young. In the photo above, the large aphid is the mother, the tiny ones daughters. Some species of aphids can telescope generations. Like Russian nesting dolls, the mother aphid has a daughter inside her who is pregnant with a daughter inside her. No wonder there are so many of them!
In fall aphids switch to a different reproduction method. The females give birth to males, mate with them, and lay eggs that overwinter and hatch as females.
Since they’re so small aphids are vulnerable to wind, rain and predators. I blew on an infested stem and watched them crowd to the leeward side. You can zap them off your garden plants by spraying them with a hose. Or you can hire some ladybugs or lacewings to do the job. (Lacewing larvae are nicknamed “aphid lions.”)
With such a bumper crop of aphids I’m on the lookout now for their predators. In this bug-eat-bug world that’s what will happen next.
Large-flowered marshallia (Marshallia grandiflora) grows in bogs and along river banks in Appalachia where it earned the common name Monongahela Barbara’s-buttons. It’s so rare that it’s endangered or threatened throughout its range and no longer grows in Maryland.
In southwestern Pennsylvania it’s found on the flood-scoured rocky banks of the Youghiogeny River where it relies on the floods to remove other species that would crowd it out. In fact, the biggest threat to Barbara’s-buttons is flood control. When the river quits flooding this plant can’t survive.
As you can see it has beautiful flowers. What you can’t tell from the photos is that the plant is 10 to 36 inches tall. From a distance the flower stands on a stalk above the leaves.
Up close the flower is intricate.
Botanists and plant lovers seek out Large-flowered Marshallia when it blooms in June.
Any parent can tell you that raising kids is hard work and even harder if there are multiple infants the same age. (Think triplets!)
Most birds experience this multiple effect every time they nest. In fact, the work is so exhausting that having “extra” kids beyond their normal clutch size decreases the parents’ life expectancy in some species.
This was shown in studies of common kestrels in Europe in the 1980s.
A team led by Cor Dijkstra artificially lowered and raised brood sizes of common kestrels by removing eggs from some nests and adding them to others. Kestrel parents whose brood size of five remained normal or was reduced to three experienced the typical winter mortality of 29%. On the flip side, adults whose broods were augmented were much more likely to die the next winter. 60% of the kestrels who raised two extra chicks were dead by the following March.
For thousands and thousands of years the clutch size of the common kestrel has been honed by the deaths of those who raised too many. The birds settled on the number five. More than that can kill them!
(photo of common kestrel nest in Germany from Wikimedia Commons. Click on the image to see the original.
Today’s Tenth Page is inspired by page 521 of Ornithology by Frank B. Gill.)