Night-Herons

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The heron family is a bit of a hodge-podge. The flamingoes, storks, ibises, Hammerkop, Boat-billed Heron, and Shoebill are often included but sometimes separated out into their own group(s). Genetic similarities will aid in the development of a taxonomy based on heritage. Historically tall, long-legged birds that generally hang around wetlands have been lumped in a larger “heron” group – but that is changing. Consensus says that there are four heron groups that are similar enough to be grouped almost together – but not really together: there are (day) herons (34 species), night-herons (9), tiger-herons (5), and the bitterns (13). Egrets are just medium-sized herons, that in the US, often have predominantly white plumage. On a world-wide basis the medium-sized herons (egrets) range from totally black to totally white.

Most taxonomic lists show at least 60 herons world-wide. eBird, the large data base for bird records, shows a total of 75 birds in the four heron groups. The International Ornithological Congress (IOC) says there are 72 species. So 60 to 75 it is. Some species have appeared on islands and have moved from one continent to another – whether these have become new and separate species leads to differing opinions and differing lists.

The herons will nest in colonies or separately depending on the species. Males establish a territory and display to attract and gain females and probably to repel competing males as well. The males will develop a breeding plumage that features plumes or long showy feathers. Some herons will have a single rather thick plume like a pony-tail, others will develop long loose feathers like sun-dried hair and a third group will develop aigrettes or loose flowing feathers that can be on the head, neck, or body depending on the species. It was these feathers that drove the slaughter of birds during the breeding season toward the end of the 1800s and early 1900s. This feather trade killed millions of birds – so many that feathers were often sold by the ton!

There are two common Night-Herons in the US; the Yellow-crowned and the Black-crowned. This species also extends south along the Atlantic side of South America to southern Brazil and on the Pacific side down to the Peruvian coast. They have also established on the Galapagos Islands. The bird above is on the Galapagos and is being watched by a couple Marine Iguanas basking behind it.
The Yellow-crowned Night-Heron is a rather long legged Night-Heron. They are typically birds of the salt marshes and marine shores. They tend to feed on crabs and most anything else that they can grab as they slowly work along the shore or along tidal creeks. As the name implies these birds, and this group, feed at night; though not exclusively.
The Yellow-crowned Night-Herons breed up into Massachusetts in years, or times, when crab populations are booming or when an invasive crab makes an appearance. We see them eating Fiddler Crabs and the rather new arrivals, the Green Crab and the Asian Shore Crab. The Green Crab has been in the US for about 200 years actually but has boom and bust periods. The Asian Shore Crab is now (probably) the most common crab in the Commonwealth. The population of Yellow-crowns will continue to grow in areas where the two non-native crab populations are growing. In many cases the birds will swallow the crabs but not start digestion until they have found a quiet spot where they will regurgitate their crabs and then eat them slowly.
The young of both Yellow- and Black-crowned Night-Herons are brown. In flight the Yellow-crowned is a bit more gawky and has legs that extend well past the tip of the tail. In many places the herons are most easily observed as they fly out from a roost onto a salt marsh to feed. The leg length is a characteristic easily noted in the dusk as the birds pass overhead.
This adult Black-crowned Night-Heron shows the shorter legs of this species.
In Australia and on many south Pacific island the Nankeen Night-Heron is the replacement for the Black-crowned Night-Heron. As matter of fact many taxonomists feel that they are the same bird (species). The color change is obvious but just about everything else speaks to a Black-crowned. Like many herons (and egrets) the Night-Herons will wander extensively after the breeding season. They are not really migrants but there is a post-breeding dispersal.
The plume is an accoutrement that develops in the males and females during the breeding season. This is very similar in size and shape to the plume that Black-crowned Night-Herons develop. This is a bird that will nest right in the city as does the Black-crowned. I have seen Nankeen nests along the Esplanade in Cairns, Queensland, Australia. These nests were right over the pathways and sidewalks and the birds were almost never noticed by the sun bather, walker, and the people passing by.
Though there are a few other forms of Night-Herons that could be mentioned (White-backed, White-eared, Japanese, Malayan) I’ll finish with a bird that belongs in its own taxonomic tribe – the Cochleariini – but seems to really be another Night-Heron. This is the odd Night-Heron type of bird called Boat-billed Heron. This is a South and Central American bird of wooded wetlands and mangrove swamps. It is found in the low wet areas of the continent and has a broad flat bill and develops a bushy black crest in the breeding season.

The various Night-Heron species are often geographically widespread and this results in a range of populations; perhaps some of these populations represent different species. For instance there are five subspecies of the Boat-billed Heron, four of the Black-crowned, five of the Yellow-crowned, and four of the Nankeen. Birds like this, that are strong fliers and that establish widely over the planet, are often genetically dissimilar to the original population. The longer the separation the greater the differences. Genetics will probably allow for more population/species/types of Night-Herons in the future.

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