Passenger Pigeon

The passenger pigeon, also known as the wild pigeon (Ectopistes migratorius), is an extinct pigeon species native to North America. Because of the species' migratory tendencies, its common name is taken from the French term passager, which means "passing by." Its migratory qualities are also mentioned in the scientific name. Long assumed to have been the closest relative, the physically similar mourning dove (Zenaida macroura), the two were occasionally confused, however, genetic investigation has revealed that the genus Patagioenas is much more strongly related than that of the Zenaida doves.

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Passenger Pigeon Adaptations: Passenger pigeons are a type of passenger pigeon that are adapted for speed and manoeuvrability in flight and they have a long tail, short head and neck, broad, long, and pointed wings, and specifically big breast muscles which allow them to fly great distances.

The size and colouring of the passenger pigeon were sexually dimorphic. The male was 390 to 410 mm (15.4 to 16.1 in) long, with iridescent golden feathers on the neck and black markings on the wings, and was mostly grey on the upper parts and paler on the underparts. Altogether, the female appeared duller and browner as compared to the male, measuring 380 to 400 mm (15.0 to 15.7 in). The juvenile resembled the mother but lacked the iridescence.

It was mostly found in eastern North America's deciduous forests, yet it was seen elsewhere. It bred mostly around the Great Lakes. The pigeon moved in massive groups, continuously hunting for food, shelter, and mating grounds, and used to be the largest abundant bird in North America, with a population estimated to be about 3 billion, and maybe as high as 5 billion. The passenger pigeon is a highly rapid flyer, capable of reaching speeds of up to 100 km/h (62 mph). The mast was the main source of food for the bird, although it also ate fruits and crustaceans. It roosted and bred in a communal manner, and its extraordinary gregariousness could be linked to food hunting and predator satiation.

Taxonomy

In the 1758 edition of his work Systema Naturae (the launching point of biological nomenclature), Swedish naturalist Carl Linnaeus proposed the binomial name Columba macroura for both the mourning dove and the passenger pigeon, wherein he seems to just have regarded the two similar. The tales of such birds in two pre-Linnaean books were mentioned in this composite description. One of these was Mark Catesby's explanation of the passenger pigeon, which has been featured in his 1731 to 1743 work Natural History of Carolina, Florida, and the Bahama Islands, and included the oldest featured depiction of the species.

Catesby's description was merged with George Edwards' 1743 account of the mourning dove, which was given the name C. macroura. There is no evidence that Linnaeus ever saw these birds in person, and his description is assumed to be entirely based on these earlier stories and pictures. Linnaeus withdrew the name C. macroura from the 1766 edition of Systema Naturae, replacing it with C. migratoria for the passenger pigeon and C. carolinensis for the mourning dove. Linnaeus also designated C. canadensis in the same edition, depending on Turtur canadensis, as used by Mathurin Jacques Brisson in 1760. Later research revealed that Brisson's description was centred on a female passenger pigeon.

Considering the length of the wings as well as the wedge shape of the tail, William John Swainson reclassified the passenger pigeon first from genus Columba to the newly monotypic genus Ectopistes in 1827. Since Linnaeus had completely replicated Catesby's wording when coining C. macroura, Outram Bangs proposed that this term be applied to the passenger pigeon as E. macroura in 1906. C. canadensis must take priority over C. migratoria (as E. canadensis) on an earlier page in Linnaeus' book, according to Harry C. Oberholser in 1918. Francis Hemming suggested to the International Commission on Zoological Nomenclature (ICZN) in 1952 that the specific names macroura and migratory be assigned to the mourning dove and passenger pigeon, respectively, because this was the original use of the authors whose work Linnaeus originally built his description on.

Evolution

The passenger pigeon belonged to the Columbidae family of pigeons and doves. The genus's oldest recorded fossil seems to be an isolated humerus (USNM 430960) discovered in the Lee Creek Mine within North Carolina in Yorktown Formation strata dating to the Pliocene's Zanclean stage, around 5.3 and 3.6 million years ago. The Zenaida doves have been largely suspected to be its closest living relatives, based on morphological similarities, especially the visually similar mourning dove (now Z. macroura). Most authors, like Thomas Mayo Brewer, believed that the mourning dove related to the genus Ectopistes and categorised it as E. carolinensis. The passenger pigeon is said to be descended from Zenaida pigeons which adapted to the forests of Central America's plains.

The passenger pigeon was larger, lacked a face stripe, was sexually dimorphic, had iridescent neck feathers, and had a shorter clutch than the other Zenaida species. Museum specimens of the passenger pigeon have been included in an old DNA analysis for maybe the first period in a 2002 study by American geneticist Beth Shapiro et al. (in a work focusing primarily on the dodo), and it has been discovered to become the sister taxon of the cuckoo-dove genus Macropygia. Rather, the Zenaida doves were discovered to be connected to Geotrygon quail-doves and Leptotila doves. 

Instead, a much more comprehensive 2010 study found that the passenger pigeon is most strongly linked to New World Patagioenas pigeons, such as the western North American band-tailed pigeon (P. fasciata), that are connected to Southeast Asian species throughout the genera Macropygia, Turacoena, and Reinwardtoena. This group is also connected to the Old World's Columba and Streptopelia doves (collectively termed the "typical pigeons and doves"). The study's authors speculated that the passenger pigeon's progenitors might well have colonised the New World by flying throughout the Pacific Ocean, or possibly over Beringia in the north.

Description

The size and colouring of the passenger pigeon were sexually dimorphic. It was between 260 and 340 grammes in weight. The adult male was between 390 and 410mm long. The nape, head, and hindneck were all bluish-gray. Iridescent show feathers adorned the sides of the neck and the top mantle and based on the angle of the light, they have been characterised as bright violet, bronze, or golden-green. The upper back and wings were a mild or slate grey with olive-brown undertones, which transitioned to a greyish-brown on the lower wings. The lower back and rump appeared dark blue-grey, while the higher tail-covert feathers showed greyish-brown. The larger and median wing-covert feathers were light grey in colour, with a few uneven black dots toward the end.

The wing's main and secondary feathers are indeed a blackish-brown colour, with a small white line on the secondaries' outer surface. The two middle tail feathers appeared brownish grey, while the remainder of the tail feathers seemed white. The tail pattern stood out because it featured white outer margins with blackish specks that were visible in flight. The lower throat and breast had a rich pinkish-rufous colour, which faded to a paler pink as it progressed down the belly and into white mostly on undertail covert feathers. There were some black patches on the undertail coverts as well. The feet and legs were a vivid coral red, whereas the bill appeared black. A narrow purplish-red eye-ring surrounding a carmine-red iris. The male's wing was 196 to 215 mm (7.7 to 8.5 in), his tail was 175 to 210 mm (6.9 to 8.3 in), his bill was 15 to 18 mm (0.59 to 0.71 in), and his tarsus was 26 to 28 mm (1.0 to 1.1 in).

At 380 to 400 mm in length, the adult female passenger pigeon seemed significantly shorter than the male. This was duller generally than the male, with a greyish-brown crown, forehead, and nape down to the scapulars, and far less iridescent feathers on the sides of the head as compared to male. The bottom throat and breast appeared buff-gray, while the stomach and under tail-coverts remained white. This was browner mostly on upperparts, paler buff-brown on the underparts, and far less rufous than that of the male. The back, wings, and tail were identical to that of the male, with the exception that the primary feathers' outer edges appeared bordered with buff or rufous buff.

The female's wings featured more patterning than the male's. The tail seemed shorter and the legs & feet were just a paler red than that of the male's. The iris appeared orange-red, with a greyish blue orbital ring that was exposed. The female's wing measured 180 to 210 mm long, her tail was 150 to 200 mm long, her bill was 15 to 18 mm long, and her tarsus was 25 to 28 mm long.

Vocalizations

The noise made by flocks of passenger pigeons has been characterized as deafening, and the bird's voice is harsh, loud, and unmusical. Most characterised it as twittering, clucks, and cooing, as well as a sequence of low notes, rather than a song. When constructing nests, the birds produced croaking noises, and then when mating, they created bell-like sounds. When faced with a threat during eating, some individuals would make alarm calls, and the remainder of the flock might join in during taking off.

Based on observations of C. O. Whitman's captive passenger pigeons in 1903, American behavioural scientist Wallace Craig released a series of descriptions and musical notations of this species' motions and sounds in 1911. Craig collated these records to aid in identifying potential wild survivors (since mourning doves and passenger pigeons are physically similar), stating that this "meagre material" was probably everything that would have been left on the issue.

Distribution and Habitat

The passenger pigeon formerly located east of the Rocky Mountains, from the Great Plains towards the Atlantic coast throughout the east, north of Mississippi in the south, and to the south of Canada in the north, all of which coincided with its principal habitat, eastern deciduous woods. It travelled regularly throughout this range in search of food and refuge. It's unknown whether the birds preferred specific trees or terrain, however they weren't likely limited to one kind as long as their quantities could be sustained. 

The passenger pigeon wintered from Tennessee, Arkansas, and North Carolina south to Texas, northern Florida and Gulf Coast, with flocks extending much further north as Connecticut and southern Pennsylvania on rare occasions. Large swamps, especially some with alder trees, constituted favoured wintering locations; if swamps had not been accessible, forested regions, especially those who have pine trees, provided favoured roosting locations. Passenger pigeons have also been spotted outside of their regular range, notably in numerous Cuba, Bermuda, Western states, and Mexico, especially during harsh winters. 

A few of these extralimital records might've been due to a lack of witnesses instead of the true range of passenger pigeons; North America had been an unstable continent at the time, and the bird might well have emerged anywhere other than the extreme west. Stragglers were also found in Ireland, Scotland, and France, albeit these birds could have been runaway captives or the descriptions were inaccurate.

Diet

The mast required to accommodate nesting and roosting flocks was made by beeches and oaks. The passenger pigeon's nutrition varies according to the season. It mostly ate acorns, beechnuts, and chestnuts in the winter, fall, and spring. In summers, grapes, cherries, blueberries, mulberries, cherries, and bunchberries became the most popular fruits to eat.

Worms, snails, caterpillars, and other invertebrates were also eaten by it, especially when it was reproducing. When it came across cultivated grains, especially buckwheat, it gained control of them. It had a particular fondness for salt, that it obtained from brackish springs or salty soil. 

Mast happens in great quantities in various places at distinct times, and only rarely in successive years, that's one of the explanations why the big flocks were always moving. Because the mast is generated in the autumn, there would have to be a lot of it remaining by the summer, whenever the young were being raised. Their eyesight and flight abilities let them search broad regions for spots that may give enough food for a temporary stay, but it's unclear how they found this shifting food source.

Reproduction

The passenger pigeon's movements were linked to locating spots suitable for this communally breeding species to nest and nurture its young, in addition to locating roosting areas. The number of times the birds bred each year is unknown; one appears most plausible, although some reports claim more. The nesting period was four to six weeks long. Around March in southern latitudes, and subsequently, in northern latitudes, the flock assembled to a nesting ground. The pigeon exhibited little site loyalty, and would often choose to nest in a new spot each year. The development of a nesting colony did not always happen right away after the pigeons landed on their breeding grounds, usually in late March, April, or May.

The colonies, dubbed "cities," were massive, varying sizes from 49 hectares (120 acres) to thousands of hectares, and were frequently long and narrow (L-shaped), with several portions left intact for unspecified reasons. They became rarely continuous because of topography. It's impossible to give more than estimations on the size and population of such nesting locations because no exact data were gathered, however, most stories cite colonies with millions of birds.

The largest nesting area yet documented was in central Wisconsin in 1871, when it was said to cover 2,200 km2 (850 sq mi), with an estimated 136,000,000 birds nesting there. Aside from these "cities," tales of considerably smaller flocks or even single pairs establishing a nesting location were common. The birds do not appear to have established large breeding colonies on the outskirts of their range.

Passenger Pigeon Extinct

Native Americans used to hunt passenger pigeons, but it became more common after Europeans arrived, especially in the 19th century. Pigeon meat was promoted as a low-cost food, resulting in widespread hunting for decades. Other reasons contributing to the species' decline and eventual extinction included the decreasing of huge breeding populations required for the species' survival and extensive deforestation, which devastated the species' habitat. Between 1800 and 1870, there was a steady fall, followed by a sharp fall between 1870 and 1890.

The last known wild bird was shot in 1901, according to legend. From around the beginning of the century, the final caged birds were divided into three groups, several of which were shot and surviving. On September 1, 1914, Martha, the last is the passenger pigeon extinct, disappeared at the Cincinnati Zoo. An instance of man-made extinction is the extinction of the species.

Extinction Causes

The main causes of the passenger pigeon's extinction were large-scale hunting, fast habitat loss, and the bird's unusually gregarious nature, which left it very vulnerable to the first two factors. The necessity to clear land for agriculture and increasing communities, as well as the need for lumber and fuel, drove deforestation. Between 1850 and 1910, around 728,000 km2 (180 million acres) of land were cleared for farming. Even while there are still enormous wooded areas in eastern North America that sustain a variety of animals, they were insufficient to maintain the massive number of passenger pigeons required to keep the population alive.

Small populations of critically endangered birds, including the kakapo and the takahe, had, on the other hand, been sufficient to maintain such species alive to the current day. The passenger pigeon's extinction has indeed been dubbed a "Blitzkrieg" due to the combined impacts of aggressive hunting and deforestation, and it's been dubbed one among the worst and most pointless human-caused extinctions in history. The passenger pigeon population fell underneath the threshold required to spread the species as the flocks shrank in size, an instance of the Allee effect.