Significance of Egg Coloration to Embryo Development

October 18, 2011 by  
Filed under Features

Researchers continue to debate the purpose of bird egg pigmentation, with the most popular theory being that camouflage is the main reason for the variation in eggshell colors, with the speckles and splotches of color providing protection from predators. This was the theory put forward by renowned biologist Alfred Russel Wallace in the late 19th century, a position that was challenged by naturalist Alexander M’Aldowie who believed the pigmentation of eggshells served to shield developing embryos from harmful radiation.

Wallace’s theory was the more widely accepted argument, and later research studies on this topic would be based on the fight for survival aspect that supports the necessity for Alexander camouflage. Other accepted theories to arise in subsequent years included the role that pigmentation plays in retaining heat and continuing the incubation process when the eggs are unattended, as well as signaling unpalatability to would-be egg-eaters and serving as identification for host birds that have parasitic eggs laid in their nests.

Although all these theories have merit, in a recently published review of a series of studies in the Journal of Avian Biology of 14 September, biologists Phillip Cassey and Golo Maurer of the University of Adelaide in Australia take the embryo’s view of its protective covering in offering possible explanations for the purpose of eggshell coloration. One of these explanations validates the original theory put forward by Alexander M’Aldowie where the pigmentation of the eggshell helps to filter, but not block, ultraviolet light for the developing embryo. It is interesting to note that even the darkest eggs, using the emu as an example, allow some light to filter through. It was also noted that pigmentation differs at each end of the egg, most likely to provide directional cues to the embryo, as well as to assist cells and structures in their early alignment.

As in the case of gulls, which commonly lay a clutch of three eggs, with the second egg laid being noticeably and consistently darker than the other two, the variations in eggshell pigmentation could be a significant factor in facilitating staggered hatching. Moreover, it has been proposed that the variations in eggshell coloring could assist the embryo in learning to recognize the difference between light and dark, calibrating circadian rhythms, as well as encouraging DNA repair and shaping bacterial communities within the egg. Researchers have also noted that pigmentation is affected by rainfall and weather, possibly compensating for local and seasonal conditions. Certainly, there is much still to learn about the marvelous world of birds, and with advancing science, more of these mysteries will no doubt be solved.

Sigurgeirs Bird Museum in Iceland

October 11, 2011 by  
Filed under Features

Surrounded by volcanic landforms and wetlands, Lake Mývatn, located near the Krafla volcano in the north of Iceland, is home to a wide range of birdlife, particularly waterfowl. Its rich biodiversity and intriguing geology continues to attract biologists, naturalists, geologists and bird watchers from around the world. It was in these beautiful surroundings that Sigurgeir Stefánsson was raised, and his love for birds became evident. The results of his life-long interest in birds can be viewed in the fascinating Sigurgeirs Bird Museum where his collection of more than 300 birds, representing around 180 species, is displayed.

Sigurgeir Stefánsson was born and raised on the Ytri-Neslönd farm, and spent his youth exploring his surroundings and collecting birds’ eggs. Soon he had specimens of all the indigenous Icelandic birds’ eggs, which he used to create a small natural history museum. At the age of 14 years, Stefánsson was given a bird that had been preserved by the process of taxidermy. This was the beginning of his bird collection, and any dead birds he, or his friends and neighbors found, were taken to the taxidermist for preservation.

Stefánsson’s collection grew until it had taken over his family’s house. It was later moved to a nearby shack and continued to grow, with other bird-lovers showing an interest in his work. While focusing on creating a complete collection of the birds of Iceland, Stefánsson also communicated and traded with ornithologists in other parts of the world, and his collection includes some exotic birds. He was often consulted by visiting researchers, as he had an intimate knowledge of the area and its feathered residents. He had expressed the desire to build a museum to properly display his collection for others to enjoy, but had no funds to make his dream a reality.

Tragically, in 1999 during a storm Stefánsson and his two companions drowned in Lake Mývatn as they attempted to repair an underwater cable – he was only 37 years old. To honor his memory and his accomplishments in the field of ornithology, the Aurora Charity Fund, together with members of his family, established the Sigurgeirs Bird Museum, which opened on 17 August 2008. In addition to viewing the extensive collection of birds on display in the museum, visitors can make use of the binoculars provided to spot local birds in the surroundings and on the lake, which is known for having the most species of duck to be found in one location.

Oology – The Study of Bird Eggs

June 7, 2011 by  
Filed under Features

Oology can have two meanings. It is used to either refer to the study of bird eggs, or it can be used to describe the collecting of bird eggs. Even though the name is the same, the impact on bird life and ecosystems is vastly different. Studying bird eggs allows scientists and conservationists to understand the breeding habits of various birds and their nests. Collecting bird eggs almost led to the extinction of many bird species, as it had become a popular hobby that is now illegal in most countries.

While practicing oology as a science, it was discovered that birds that nest and lay their eggs in bushes generally lay speckled eggs, as opposed to birds that have their nests on the ground and lay unspotted white eggs. It was also found that birds that choose trees as the ideal nesting spot have either greenish colored or blue eggs that can either be unspotted or spotted. This gives conservationists great insight into birds, their nests, amount of eggs laid and general nesting habitats of various bird species.

Collecting eggs was seen as a hobby, much like collecting stamps, during the nineteenth and twentieth century. This led to a rapid decline in birds and near extinction of some. Collectors did not just remove one egg from the nest, but the entire clutch of eggs. The rarer the bird, the more valuable their eggs became, and this endangered them even more. After the eggs were collected, they would be blown out, their contents removed, to prevent the rotting of the eggs. Egg collectors would then write a date on the egg, identify the specie and frame the eggs. It is for this reason that oology as a hobby has become illegal and in certain countries, collectors can face imprisonment.

In Britain, an overzealous oologist named Colin Watson stole the eggs out the nests of very rare and protected bird species and was fined numerous times for collecting eggs. He fell to his death from a tree in 2006, and it was revealed that he had a collection of more than two thousand eggs in his possession. Gregory Wheal, also from Britain was jailed for six months for being in possession of raven and peregrine falcon eggs, and fellow Brit, Richard Pearson had more than seven thousand seven hundred eggs, which are now protected by the law, and his detailed notes and confession described a fifteen year period of stealing eggs. Fortunately, the oology hobby became less popular and oology is now used to introduce new captive breeding methods, incubation and to save endangered species from extinction.

Warblers Ward off Imposters

April 19, 2011 by  
Filed under Features

Cuckoos have never been very popular amongst other birds species. They are known to be lazy parents and have become sophisticated in their methods of camouflaging their own eggs to look like those of other species, so that they are able to introduce their own eggs into the nest and have the other birds raise their chicks. But host birds are beginning to wise up to the counterfeit eggs being laid in their nests and have developed their own skills to fight off imposter eggs.

Studies conducted at the University of Cambridge, led by Claire Spottiswoode, revealed that host birds, especially warblers, have become more vigilant in regard to recognizing imposter eggs. Most birds use one of two methods. They either teach themselves to be able to recognize the imposter eggs purely by sight, or they have taught themselves to change the coloring of their own eggs, making it more difficult for the cuckoo to copy. During the research studies, scientists placed the eggs in the nests of bird species that were closely related to warblers. It seemed to show that the red-faced cisticola was quite apt in noticing an imposter egg purely by sight, while the tawny-flanked prinia was not very confident in noticing a difference. In its defense, the prinia is able to lay a rainbow color of eggs, complete with variable patterns, which deter cuckoos from the challenge of laying eggs in their nests. In addition they are able to recognize the imposter egg due to their defenses and eject the eggs immediately. The rattling cisticola is no longer the target of the cuckoo, as it has been able to use both defenses, that of recognition and color changing of eggs, to establish which of the eggs are imposters.

Researcher Dr. Martin Stevens expressed his findings of the outcome of the studies, saying: “Our experiments have shown that these different strategies are equally successful as defenses against the cuckoo finch. Moreover, one species that has done a bit of both – the rattling cisticola – appears to have beaten the cuckoo finch with this dual strategy, since it is no longer parasitized. The arms race between the cuckoo finch and its host emphasizes how interactions between species can be remarkably sophisticated especially in tropical regions such as Africa, giving us beautiful examples of evolution and adaptation.”

Raising a Chick at the Age of Sixty

March 15, 2011 by  
Filed under Pet Birds

Wisdom’s first band was placed on her while incubating an egg in the year 1956, and the U.S. Fish and Wildlife Service have been keeping an eye on her ever since. To be able to breed, a Laysan Albatross needs to be five years old, which now puts her age at an estimated sixty years. Wisdom is a celebrity of the North American Bird Banding Program, as she is the oldest bird on their records since the project was initiated ninety years ago. Now she is raising another chick, which brings her total number of chicks raised during her lifetime to approximately thirty to thirty-five. What is even more amazing, is the fact that these birds mate for life, meaning that her partner is either still accompanying her on her journey or she has outlived him.

The albatross has a long history with mankind, with sailors believing that each albatross was the soul of a lost sailor and thus they were extremely opposed to these birds being killed. The relationship between birds and humans might have changed somewhat, but they are still being studied and protected.

Not only is the new chick that Wisdom is raising a wonderful landmark event, but she has been a great source of information for researchers and scientists. Her estimated age is determined by the life cycle that the Laysan Albatross follows. Parents will raise a chick for an entire year, and once the chick is fledged, it heads out to sea for time period of between three to five years. These amazing birds will not touch ground during this time and are even able to take a small nap while they are flying. Due to these birds traveling a distance of around fifty thousand miles in a year, Wisdom has traveled an estimated two or three million miles already. She has most definitely used her wisdom to survive all these years.

Bruce Peterjohn could not be prouder of Wisdom, and as the North American Bird Banding Program chief, he was able to confirm that the second oldest Laysan Albatross that was recorded by the project was banded as a chick and lived to forty-two years and five months. And while Wisdom silently sits with her chick and continues on her journey, still looking fit and healthy, she has no idea what a stir she has caused amongst the humans who have been following her life and how proud and excited they are for her.

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