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Significance of Egg Coloration to Embryo Development

Editor — Tue, 18 Oct 2011 10:40:08 +0000

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

Editor — Tue, 11 Oct 2011 11:12:48 +0000

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

Editor — Tue, 07 Jun 2011 11:52:33 +0000

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

Editor — Tue, 19 Apr 2011 12:09:07 +0000

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

Editor — Tue, 15 Mar 2011 12:53:10 +0000

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.

Bird Breeding

Editor — Mon, 09 Feb 2009 12:50:35 +0000

Bird breeding generally begins as the daylight hours of summer increase. Territorial behavior becomes evident with males selecting and defending their territory by means of singing and flight displays. Territories vary in size depending on availability of food and requirements of birds breeding in the area. When a female enters a male’s territory she may be threatened by him as if she were another male. However, she will not fight back or fly away if she is ready to mate, and copulation will take place.

The first eggs are usually laid the day after the breeding pair completes the nest. Eggs may be laid daily or on alternate days, even up to five day intervals depending on the species. For the breeding of birds to be successful, the eggs must be incubated. The parents transmit heat to the eggs by means of brood spots (bare patches on underbelly with many blood vessels). Eggs are turned as often as 12 times an hour and incubation periods vary according to species. When they hatch, some chicks are completely dependent on their parents, these are called altritial. Others are able to run and feed themselves immediately, and these are called precocial.

Many people are interested in finding out about bird species breeding in their area. Studies are conducted and breeding bird atlases are produced which will provide this information. If for example you would like to find out about a British bird’s breeding habits, you would consult a breeding bird atlas for Britain.

The basic concepts discussed above also apply to breeding birds in captivity. For example, when breeding love birds it is important that they receive the correct amount of sunlight so as to stimulate breeding. Breeding love birds can be done in aviaries or individually in bird breeding cages. Bird breeding cages must have enough space for the birds to move around comfortably and continue with normal behaviour. Ensure that breeding pairs are fed properly so that they remain in good condition and that the eggs will not have defects. Once the young hatch, they too require suitable nutrition.

Breeding, whether in captivity or in the wild, is vital for the continuation of bird species and our continued pleasure in these beautiful feathered creatures.

The Pleasure of Pet Duck Ownership

Editor — Wed, 16 Jan 2008 10:20:09 +0000

When seeing a cute little duckling, many an animal-lover is tempted to pick it up, cuddle it and take it home. This urge can become almost impossible to resist if the animal-lover is accompanied by children. Ducks make wonderful pets, but before making a commitment to care for a pet duck that could be around for up to twelve years, it is wise to give the matter careful thought, weighing up (and even writing down if necessary) the pros and cons of adding this fluffy little bird to the household.

Experts readily agree that ducks are very sociable birds and, unless the owner has loads of time to spend with it, they should not be raised alone. Ducklings should be bought as young as possible in order for the owner-pet bond to be strong. A duckling will adapt to the household and other pets fairly easily if introduced at a young age. Some duck owners even adopt their pet birds as eggs and act as mother from the time the little duckling emerges. Once that bond is formed, it is permanent and can be very rewarding.

Ducklings raised without their mother must be given an artificial heat source for the first four to five weeks of their lives. This can be provided by a heat lamp positioned in one corner of the enclosure, with sufficient room for the ducklings to move away if they get too hot. Many have found that a vinyl child’s pool on a wire frame works well. This can always be used as a swimming pool for the ducklings when they are a bit older. The duckling’s area should be lined with an absorbent material such as wood shavings, and droppings must be picked up on a daily basis – a cat litter scoop will do the job.

Ducklings can be fed on game bird starter which is found at most farm supply stores. Chick starter food is not suitable for ducks as it does not have the correct nutrients for development. Ducklings also need some fresh chopped vegetable greens daily. Mixed greens from the green grocer and weeds from your garden will give them what they need. Ducks must always have a supply of water nearby when they are feeding. They use this to wash the food down and they need to keep the vents on their beaks clean. Bread, popcorn and chips should be considered as junk food and not given to ducks. They will thrive on garden bugs, snails, worms of all descriptions, mosquito larvae and whatever creepy crawly comes their way. Ducks are adept at catching flies and mosquitoes that may buzz by. Absolutely no pesticides should be used in a garden that is a duck’s feeding ground. A duck’s garden diet should be supplemented with cracked corn, floating coy food and fresh vegetable trimmings.

Once the ducklings are old enough to move outside they must have some type of shelter from the elements and sufficient water to allow them to dip their heads right under. This is necessary to prevent their eyes becoming dry which could lead to cataracts.

Duck owners will agree that not only are these lovely birds good and loyal pets, they are useful too by ridding the garden of pests. So if you have what it takes to be a duck owner, you can be sure of years of love and entertainment from your feathered friend.

The Bane of Brood Parasites

Editor — Mon, 17 Dec 2007 12:52:08 +0000

When we hear the word “parasites”, most of us would assume it is referring to an organism that feeds off another. In brood parasites, in the avian world, it works a little differently. To put in laymen’s terms, it is when one bird species lays their eggs in a different species‘ nest, so that the parasite species do not have to take care of their young. Over the years, host bird species became wise to the brood parasites, but as a parasite does not give up that easily, the brood parasites have come up with various devious plans to fool the hosts.

Brood parasitism can be found in insect species as well as fish species. But in avian species there are two different types of brood parasites. Non-obligate brood parasites will lay their eggs in host nests of the same species, such as the African Weaver and the Bank Swallow. Obligate brood parasites will lay their eggs in other species nestsm and examples of obligate brood parasites include the Bronzed Cowbird, European Cuckoos and African Honeyguides.

Host species started to notice the difference between their eggs and the parasite eggs, and began to eject them from their nests. To overcome this problem, parasite species started to mimic the host parents’ eggs, so that the difference between the host egg and parasite egg would be almost impossible to tell apart. Some parasitic species have become so advanced that they are able to mimic a variety of species eggs, such as the Brown Headed Cowbird, giving the parasite a choice of hosts. One of the most successful brood parasites is the Common Cuckoo that is able to mimic the eggs of the Meadow Pipit, Brambling, Streaked Laughing Thrush, Great Reed Warbler and Meadow Bunting to such perfection that scientists need to look at genetic markers to tell them apart.

In most cases, the parasite hatchling is much larger than the hosts’ hatchling. The parasite chick will often kill the host chick or kick it from the nest. It has even been noticed that host species are threatened into caring for the parasite hatchling. In some cases, the host has ejected the parasite chick from the nest, and in retaliation the brood parasite adult has destroyed the hosts’ nest. The aggressive behavior of the brood parasite, of which most remain close to the host nest to keep an eye on their eggs, then forces the often-smaller host to care for the parasite hatchling.

Scientists are still working on projects and studies regarding this very interest form of survival, the impact it has on the host population and trying confirm their intimidation theories across the board. But, when looking at brood parasites in general, it seems that the host species always suffers, and the only party that gains from this arrangement are the brood parasites.

A Closer Look at the Intriguing Galapagos Hawk

Editor — Fri, 12 Oct 2007 11:49:57 +0000

The Galapagos hawk is found exclusively in the Galapagos Islands. The adult Galapagos hawk is almost completely different shades of brown and the female is larger than the male with an average size of 56 cm in length. It is one of the few terrestrial predators on the islands and has no natural enemies.

Their nests, which they usually build in trees, become fairly large over time as they are re-used at each breeding season, with some new twigs added each time. The Galapagos hawk has earned a reputation in the avian world as a notorious non-conformist due to its rare mating system known as polyandry – one female with multiple male mates. The Galapagos hawk female is known to have up to four mates at a time. This unusual mating system is reportedly only found in 12 out of 9,000 bird species in the world. All the males in the relationship assist in caring for the eggs and the hatchlings.

The Galapagos hawk is both a hunter and a scavenger. No other bird of prey is known to be as fearless as the Galapagos hawk as it hunts down just about anything smaller than itself that moves including lizards, young iguanas, doves, rats, centipedes, grasshoppers and other birds. As a scavenger it will also feed on virtually any dead animal such as marine iguanas, sea lions, sea birds and even fish that may wash up on the beach. The young Galapagos hawk is known to be very curious and visitors may find a Galapagos hawk getting too close for comfort in order to take a good look.

The Swainson’s hawk, which resides in the prairie regions of North America, migrating annually to South America for the winter months, is the closest relative of the Galapagos hawk. Because of their nearly identical mitochondrial DNA, they are often referred to as sister species. It is feasible that the Swainson’s hawk could have been blown off course during its annual migration and landed on the Galapagos Islands off the coast of Ecuador, thereafter adapting to its environment. Despite the close genetic relationship between these two hawks though, unlike the Galapagos hawk, the Swainson’s hawk is a monogamous breeder. More recent research being carried out on the DNA sequences of feather lice taken from the Galapagos hawk is giving further insight into its evolutionary history. By tracing the family tree of the feather lice, scientists are demonstrating how symbionts of larger species can reveal a great deal about the history of that species. It will be interesting to see what future discoveries will be made about this interesting bird, the Galapagos hawk.

The Bad Habits of Cowbirds

Editor — Fri, 29 Sep 2006 13:10:44 +0000

Cowbirds have an unusual life strategy: they lay their eggs in other birds species‘ nests. North America’s Brown-headed Cowbird first evolved this strategy in order to follow herds of buffalo. The cowbirds fed on insects flushed up by the buffalo’s feet. As the buffalo migrated around the Great Plains, the cowbirds followed- even during the birds’ breeding season. If the cowbirds took care of nests, they couldn’t follow the buffalo. So they left their eggs behind in other songbirds’ nests.

Buffalo are now scarce in North America, but cowbirds’ numbers have exploded. They now follow grazing cattle, and also benefit from land cleared for farming. Once confined to the Great Plains, their range now covers most of North America.

Many wildlife managers are very concerned about cowbirds- they create a real problem for other songbirds. In one year, a single female cowbird may lay eggs in 40 different nests. At least 144 different species of birds have unknowingly raised a cowbird’s chick.

Some host birds don’t fall for the cowbirds’ trick: they’ll break open the cowbird’s egg, or will abandon the nest entirely. But others do not notice the newcomer. When the cowbird chick hatches, it usually crowds out the true chicks, by taking most of the food brought by the mother songbird.

Cowbirds share this habit of nest parasitism with a few other bird species, such as the cuckoos of North America and Europe.