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Mystery Unlocked: Bird Egg Shapes and Flight Ability are co-related, says Study

The analysis revealed that birds tend to lay eggs that are more asymmetric and more elliptical if they are better fliers

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Bird egg
Different shapes of bird eggs. Pixabay
  • Team of researchers has found that the egg shape is related to flight ability
  • The team used photographs to analyze the shapes of nearly 50,000 eggs representing 1,400 species.
  • The egg membrane may also play a critical role in determining the shape

New York, June 24, 2017: In what could perhaps crack the long-term mystery behind the astonishing variety of bird egg shapes, an international team of researchers has found that the egg shape is related to flight ability, with good fliers tending to lay pointy or elliptical eggs.

Avian eggs have fascinated humans for millennia because they come in different shapes — elliptical in hummingbirds, spherical in owls, pointy ovoids in shorebirds and almost everything in between. But we still lack the answer to this simple question — why did different egg shapes evolve, and how?

The new study published in the journal Science suggests that egg shape is related to flight ability, and that the egg membrane may play a critical role in determining shape.

“In contrast to classic hypotheses, we discovered that flight may influence egg shape. Birds that are good fliers tend to lay asymmetric or elliptical eggs,” said the study’s lead author Mary Caswell Stoddard of Princeton University in New Jersey, US.

“In addition, we propose that the stretchy egg membrane, not the hard shell, is responsible for generating the diversity of egg shapes we see in nature,” Caswell said.

To unravel the mystery of egg shape, the researchers used a multi-step, multidisciplinary process, applying tools from computer science, comparative biology, mathematics and biophysics.

First, the team used photographs to analyse the shapes of nearly 50,000 eggs representing 1,400 species.

The eggs, from the online database of The Museum of Vertebrate Zoology at Berkeley, came from across the globe and were largely collected by naturalists in the late 19th and early 20th centuries.

Using computer code, the researchers quantified each egg’s asymmetry and ellipticity.

By combining the power of high-throughput digital image analysis with the wealth of data in the museum egg collection, the team was able to map the world of egg shapes.

The team then developed a biophysical model to explain how processes in the bird’s oviduct might generate different egg shapes.

The team also used an evolutionary framework to test hypotheses about egg shape.

Using a recently constructed phylogeny, or family tree, of birds, the researchers compared egg shapes across different bird lineages. In this analysis, they included details about nest type and location, clutch size, diet and flight ability.

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The analysis revealed that birds tend to lay eggs that are more asymmetric and more elliptical if they are better fliers.

The researchers suggest that as birds’ bodies became adapted for powered flight, this resulted in morphological changes like reduced body size and a reduced abdominal cavity.

The discovery that morphological constraints associated with flight may contribute to egg shape challenges the conventional wisdom that egg shape is largely influenced by clutch size or nest location. (IANS)

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Sambhar Lake Becomes Death Bed for Large Number of Birds

The excessive salt in the water led to the poisoning, causing hypernectremia, which is water deprivation due to sodium intoxication

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Sambhar Lake
After witnessing drought for many years, this year the Sambhar Lake, however, brimmed with water due to heavy rains. The inflow made the water toxic due to the change in its alkalinity. Pixabay

A deadly game of survival is on in the Sambhar lake of Rajasthan for decades — salt versus birds. The result came a few days back: thousands of birds were seen floating dead in the lake and their carcasses scattered on the edge of the 12 km catchment area.

The dead birds seen floating in this largest inland salt lake in the country, include plovers, common coot, black winged stilt, northern shovelers, ruddy shelduck, and pied avocet among many other migratory birds.

Harsh Vardhan, a renowned environmentalist, told IANS that no forest department official has ever been appointed to look after the lake. The lake comes under the Hindustan Salt Limited, a public limited enterprise formed in the post independence era to manufacture salt. Its job is to manufacture salt. So who should look after the lake; this has never been decided, he said.

The lake has not been handed to the forest department, and the area, where birds come, is no one’s land. Sambhar lake may be a part of the Hindustan Salt Ltd, but the company has nothing to do with the birds, he says.

The chief wildlife warden Arindam Tomar has maintained silence over the issue.

Even, Principal secretary, forest and environment Shreya Guha has washed her hands off the issue. All that she did was to a give statement that the Jaipur and Nagaur District Collectors have been asked to remove the bodies. She added that 4,800 birds have been dead till date, which is disputed by experts like Harsh Vardhan, who say that counting is not easy in the vast area.

Chief minister Ashok Gehlot on Thursday held a meeting on the issue.

Sambhar Lake
A deadly game of survival is on in the Sambhar Lake of Rajasthan for decades — salt versus birds. Pixabay

Meanwhile, Harsh Vardhan questioned the presence of several private salt miners and entrepreneurs, who have set shops in and around the lake. “They dig tube wells which suck water from the land making it parched. The remaining water gets evaporated leaving crystal of salts which are packed and sold in gunny bags,” he said.

Lack of water and drought has haunted Sambhar lake for years. State government has been spending huge money to woo tourists through activities like mobiking, balloning, race, Bollywood shoots, etc. A resort on the rim of the lake showcases salt manufacturing for the tourists. Crores of Rupees have been spent on the upkeep of the narrow gauge train and watch stations, but birds and conversation issues were always overlooked.

As Sambhar lake went dry, concentration of salt deposits came up within it. The water from surrounding rivers, meant to flow into the lake, was diverted by the miners.

After witnessing drought for many years, this year the lake, however, brimmed with water due to heavy rains. The inflow made the water toxic due to the change in its alkalinity.

The excessive salt in the water led to the poisoning, causing hypernectremia, which is water deprivation due to sodium intoxication, Vardhan said.

It seems birds which came in high numbers due to high water quantity this season died due to hypernectermia after consuming their feed which is the planktons, the microrganisms found in water.

Sambhar Lake
The dead birds seen floating in this largest inland salt lake i.e Sambhar Lake in the country, include plovers, common coot, black winged stilt, northern shovelers, ruddy shelduck, and pied avocet among many other migratory birds. Wikimedia Commons

The only step that has ever been taken by any government in the state was in 1981 when it was decided to designate the site as wetland and was renamed as the Ramsar site.

According to an estimate, around 60,000 birds visited the lake in a year which has come down to less than 20,000.

Vardhan says that if the lake remains with the Hindustan Salt Limited, which has been a loss making unit since years or if it is handed over to the private operators, who do excessive mining of water, then the lake and the birds are sure to die.

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Experts like him want the lake to be handed over to the forest department which can develop it as a wetland. (IANS)