The pink egret (Egretta garzetta) is a relatively small white heron. It is a resident breeder in parts of Asia, Australia, and New Zealand and is a rare vagrant to Western Europe, especially Britain. As its name suggests, some individuals have a distinctive pink tinge to their plumage, making them stand out among other white herons and egrets. But just how rare are these pink morphs? Let’s take a closer look.
What causes the pink coloration?
The pink coloration seen in some egrets is caused by an uncommon genetic mutation. This results in an overexpression of the color pigment phaeomelanin, which also gives Flamingos their distinctive hue. Normally egrets have bright white plumage, but the mutation causes pink phaeomelanin to be deposited in some of their feathers.
This phenotype is known as color morphism. The morphism that causes the pink color is thought to occur randomly in egret populations at a very low frequency. The mutation only produces a partial pink coloring, rather than uniformly pink feathers across the entire bird. Generally, the pink morph egrets have pink on their back, wings, breast and neck areas. Their beak and legs remain the yellow color.
How rare are pink egrets?
Pink egrets are exceptionally rare globally. They occur at a frequency of less than 1 in 1000. For example, in a survey of Egretta garzetta populations across India, only 3 pink individuals were recorded out of an overall population of more than 2500 birds examined.
Similarly, in Australia pink morphs may occur at a rate of 1 in 3000-5000. A survey of White Egrets in New South Wales recorded just 15 pink individuals out of a population of over 35,000 birds.
Across the global population, the frequency is likely around 1 in 5000 birds or 0.02% exhibiting some degree of pink coloration. So spotting a pink egret in the wild is a very uncommon sight indeed!
Why are pink morphs so rare?
The low frequency of the pink mutation is likely for two key reasons:
1. The genetics behind the coloration
The pink morphism is caused by a recessive gene. This means an egret needs to inherit two copies of the mutated gene, one from each parent, in order to express the pink coloration. As the mutation occurs randomly at such a low frequency, the chances of two birds with the recessive gene mating and producing a pink chick are very slim.
If only one copy of the mutated gene is inherited, the egret will remain white. The mutation can be carried hidden in populations for generations before two carriers coincide and produce a pink fledgling.
2. Lower fitness and survival
The second key factor is that the pink coloration may actually confer some survival disadvantage. While the bright pink plumage might seem striking to human observers, it could make the egrets more visible to predators. There are also metabolic costs associated with overproducing the pink pigment.
These fitness costs mean pink egrets are likely selected against by natural selection over generations. So even when pink individuals are born, they may experience higher mortality rates and be less likely to successfully breed and pass on the mutation. Over time, these evolutionary pressures keep the frequency of pink morphs extremely low.
Where can pink egrets be spotted?
While a pink egret can turn up anywhere in their global range, some hot spots have emerged:
India
Small numbers of pink egrets have been spotted at wetlands in southern and eastern India, such as near Bangalore and Bhopal. The Kerala Backwaters region is a particular hot spot.
Australia
Pink morphs have been recorded in wetlands across northern, eastern and southern Australia. Good sites include Kakadu National Park, Broome, and the Macquarie Marshes in New South Wales.
New Zealand
New Zealand’s extensive wetlands provide habitat for white egrets, and a handful of rare pink individuals have been sighted over the years. Tauranga Harbour and Farewell Spit are promising birding sites.
Indonesia
The islands of Indonesia have a number of resident egret populations, with occasional pink individuals reported from Java, Bali, Sulawesi and Sumatra.
Elsewhere
There are very sporadic reports of pink egrets from other parts of the range, including Thailand, China, Japan, and Palau. Sightings across Europe and the Americas are exceptionally rare.
Conclusion
The pink color morph seen in small numbers of egrets is caused by an uncommon genetic mutation. Globally, only around 1 in every 5000 white egrets exhibits some degree of pink plumage. Their rarity is due to the recessive nature of the gene and probable lower survival rates. While scarce, dedicated bird watchers have the best chance of spotting these exotic pink-feathered egrets in wetland habitats across Australasia and Asia. A pink egret sighting remains one of the most prized birding experiences across their range.
