Passenger Pigeons

Alex Re (00:00): Hello, welcome to On Wildlife. I'm your host Alex Re. On this podcast, we bring the wild to you. We take you on a journey into the life of a different animal every week, and I guarantee you, you're going to come out of here knowing more about your favorite animal than you did before. This week we're talking about an animal whose relatives I'm sure you're familiar with. Unfortunately, these animals were driven to extinction, but they were still around in the 19 hundreds, so we have a good amount of information on them, but they can also hold the key for how we can bring animals back from being extinct. So let's hop in a time machine as we travel back to the early 20th century to talk about passenger pigeons.

(01:01): The passenger pigeon whose scientific name is ECTs. Migrator is a recently extinct species of migratory bird. They were native to North America, although now extinct. This species is estimated to have numbered in the billions of individuals at the height of their population. This bird went extinct early in the 19 hundreds, almost completely due to human exploitation, and don't worry, we'll get into all of those details later on in the episode. Passenger pigeons were relatively large birds compared to the rest of their relatives, and this is partially the reason why they were driven to extinction by humans. They were also very well adapted to moving quickly through their environment with broad wings and a pointed tail being highly migratory birds. They had very large breast muscles so they could fly the long distances they needed to. This is what made people want to hunt them. They had more meat than the average bird.

(02:00): They were about 16 inches long and weighed up to 12 ounces. Passenger pigeons belong to the family Columba day, which is pigeons and doves. Their closest living relatives are the band tailed pigeon and the mourning dove. The only member of their family that's larger than them is a species of turtle dove. These birds were relatively long lived and in captivity lived to at least 15 years old. Martha, the last living passenger pigeon was at least 17 and could have been as old as 29. There are many common misconceptions about passenger pigeons. For starters, people thought that they were almost exclusively dependent on acorns. While acorns did make up a significant portion of their diet, they also fed on a myriad of other plants and animals. Two other major parts of their diet were beach nuts and chest nuts. However, the American chestnut began to go extinct in the early 18 hundreds.

(03:03): This misconception about acorns is also disproven as these pigeons had been abundant during periods of history when acorns weren't passenger pigeons had been observed feeding on 42 genera of plants and seeds, they would eat seeds and plants in the fall, winter, and spring, and they would also feed on crops when available, which is partially the reason why they were viewed as a major pest. In the summer when they required a higher amount of energy, they would feed on fruits and insects. They could eat worms, snails, and caterpillars, and they needed these high energy foods for breeding and feeding. Their young salt was also a very important part of the passenger pigeon's diet, and they had been observed sipping from brackish springs or ingesting salty soil. Okay, let's take a quick break, but when we get back, we'll talk all about their social structure and behaviors. The science words that I want to tell you about today are classical conditioning. This is a psychology term that means learning through association. A classic example of this is Pavlov's dogs, where Pavlov would ring a bell every time he was going to feed his dogs. Then he started to ring the bell without feeding them and the dogs would start to salivate, meaning that they knew the food was coming.

(04:46): Okay, welcome back. Passenger pigeons demonstrated sexual dimorphism between the male and female, which is very rare for members of the family Colomba day. This means that the male and female look different from each other. The male had a red underbelly with a blue gray coloring on its head, body, and wings. While the female was a brownish color with a gray white underbelly. The only characteristics that the male and female shared were red eyes, black bills and red feet. Their courtship took place in early spring, particularly late March, April and may. These birds nested in massive colonies. The colonies were so big that they were called cities and they could range up to thousands of acres in size. These colonies were arranged, so the area they took up was a very long but narrow strip of land. Like many birds, passenger pigeons had a courtship ritual or mating dance in which the male would try to gain a female's affection.

(05:50): These displays usually took place on a branch and consisted of the male making vocalizations and certain movements. These vocalizations are described as a tech sound. The male would hold onto his perch tightly and flap his wings as if he were trying to fly away without actually flying. The male would then press his head and body against the female, and if the female decided that he was worthy, they would become a monogamous pair returning to each other year after year when courtship and mating was complete, a female would lay a single white egg in a nest of twigs that was about a foot in diameter. Passenger pigeon eggs and hatchlings developed quite quickly. A passenger pigeon egg would be done incubating in only 12 to 14 days. The passenger pigeon chicks were also ready to leave the nest and fly at only 14 days old. When they were born, the chicks were featherless and blind and the rapid development of their young was an adaptive trait, so the massive colonies of pigeons would not be around long enough to deplete the local food supply.

(07:03): There are some accounts that these birds would nest up to twice per season. And remember when I said these colonies were huge? Well, a single tree could be the host to over a hundred passenger pigeon nests. A report from Wisconsin estimated that a nesting colony was as large as 850 square miles in size and hosted 136 million birds. Passenger pigeons could be described as a hyper social species. The historical accounts give reports of these birds being so hyper social that they would line every branch on a single tree and would even perch on each other's backs. They would roost so densely in trees that smaller trees would bend to the forest floor under their weight. This leads to another misconception that these pigeons required massive flocks just to survive. The main arguments for this view is that in small flocks, they couldn't effectively breed escape predators or find food.

(08:05): In reality, passenger pigeons did just fine in smaller flocks, and they were observed breeding in the wild. In single pears, they primarily inhabited deciduous forests east of the rocky mountains, and depending on the time of year, they ranged from Central Canada all the way down to Arkansas. Due to the size of their flocks, they needed extremely strong trees to support them. They preferred beach and oak for nesting and roosting in the winter. They preferred swamp habitats with large alder trees, and this is partially because swamps are usually warmer than regular forests. If these swamps were not available, they chose strong pines in the winter to roos being a migratory bird. They didn't spend the whole year in one area. In the winter, they would fly south to roost from Arkansas, Tennessee, and North Carolina, even to Texas there were even some sightings as far south as Bermuda, Cuba, and Mexico. In the summer, they inhabited the South Canadian regions of Quebec, Ontario and Nova Scotia. Now knowing that passenger pigeons are extinct brings up a lot of questions. Were they important to the ecosystems that they live in? Are our ecosystems different now that they're gone? We'll find out right after the break

(09:39): Time for today's trivia question, where on earth did the meteor that killed the dinosaurs make impact? The answer is the Yucatan Peninsula in Mexico.

(10:07): Passenger pigeons were a force for ecosystem change and health. When they were alive, some sources refer to them as ecosystem engineers because of how large of an impact they had on the environment. Because of their huge flocks, they would essentially rip through forests that they inhabited and create significant destruction in their wake. They would break branches and saplings off because of the sheer weight of the flocks roosting in them, and they would also leave guano a k a bird poop behind that can reach up to a foot in depth. The guano was an important source of nutrients to kickstart the forest regeneration process like ash. After a forest fire. There had also been reports that trees up to two feet in diameter would be snapped off only a few feet from the ground. Imagine how many pigeons it would take to do that. Through this destruction, they altered the forest landscape and gave opportunity for different stages of succession.

(11:08): This is extremely important because a healthy forest needs to have areas that are disturbed and rebuilt every once in a while. These types of forests support high levels of biodiversity and an overall healthy ecosystem. Passenger pigeons were also an important source of food for many animals like hawks, owls, eagles, snakes, weasels, wolves, skunks, and foxes. While they were preyed upon by many animals, their predation had little to no effect on their populations just because of the sheer number of individuals. The size of their flocks was actually an effective defense mechanism as it deterred animals from attacking them. But unfortunately, we found a to deplete their population all the way down to zero. So what happened? The last member of the species died in 1914 in captivity, and the last known wild individual was shot in 1900. The man who shot the last known passenger pigeon did not come forward about what he had done until he was over 90 years old because of the guilt that he felt.

(12:17): Not only was this species a victim of overharvesting, it was also one of the first species to fall victim to mass commercialization. Due to the development of America's railways, pigeon meat and products could be shipped anywhere, and their harvesting was no longer a local practice to feed a village, but was a commercialized industry. No one at the time really cared that the passenger pigeon numbers were declining because not only were they a commodity, but they were also thought of as a major pest. The flocks would ravage agricultural products and damage buildings and trees due to their size. They also left behind huge amounts of their waste, and because of how large their populations were, nobody thought that they were in any trouble of going extinct. People would shoot net grab and hit hundreds out of the sky at a time, and there are even reports that you could stick a pole into the air when a flock was overhead and pigeons would fall out of the sky.

(13:18): The flocks were so large and dense that they would block out the sun for hours at a time. It's sad that we'll never know what our forest ecosystems were like when passenger pigeons were around or will we? Although the passenger pigeon is extinct today, there are meaningful steps being taken to try and bring them back. An organization known as Revive and Restore started a passenger pigeon de-extinction program in 2012. The goal of this program is to genetically engineer this species back into existence using passenger pigeon, d n a and close living relatives. This program's goal is not for commercial or profit reasons. It's for advances in conservation and genetic engineering. The general idea of the project is to splice passenger pigeon d n a into the genome of a close living relative the band tailed pigeon. This is an interesting process because it requires that the scientist figure out what parts of each D n A sequence actually code for something.

(14:23): Because a lot of D N A is junk and doesn't really do anything, they also have to figure out what parts are the same between species and what parts make the species different from each other. They then take the parts of the passenger pigeon d n a, that differ from the band tail pigeon and insert them into the band tail genome effectively making a passenger pigeon stem cell that can then be used to grow an embryo. These passenger pigeon cells then be injected into an early stage rock pigeon embryo. When injected, they'll colonize the embryo's reproductive system, and when the egg hatches, it'll hatch what is called a chimera rock pigeon. These chimeras can produce offspring that are regular rock pigeons, rock pigeon, and passenger pigeon hybrids, and true passenger pigeon offspring. This is the stage that has been reached as of 2019. However, the Kymera Rock pigeon only has a one in a hundred thousand chance of producing a passenger pigeon, so more work is to be done.

(15:27): Passenger pigeon offspring will first be raised by surrogate rock pigeon or band tailed pigeon parents. Once there are enough passenger pigeon individuals, they'll begin raising their own offspring. It'll be interesting to see how the pigeons raised by the Surrogate Parents Act because both surrogate parents species have very different behaviors from natural passenger pigeons. This will be a great example of whether or not certain behaviors are nature or nurture. Small groups of passenger pigeons will be released into large controlled aviaries to see how they interact with the natural environment. The end goal of this project is to eventually release passenger pigeons back into the wild as a step towards more effective forest conservation. As I talked about earlier, this species used to be a major contributor to the health of the forest, and its extinction is a possible reason. Our forests today aren't in great shape.

(16:26): This project is ambitious and has already made great strides in breaking scientific barriers. If it's completed in full, it'll be one of the greatest achievements in genetic engineering, science and science as a whole. In history. If you want to help with the de-extinction of passenger pigeons, you should check out Revive and Restore. You should also take a look at the American Bird Conservancy and the Wildlife Conservation Society to make sure that what happened to passenger pigeons doesn't happen to any other birds. Thank you so much for coming on this adventure with me as we explored the world of passenger pigeons. You can find the sources that we use for this podcast and links to organizations that we reference at onwildlife.org. You can also email us with any questions at On Wildlife dot podcast@gmail.com, and you could follow us on Instagram at On Wildlife or on TikTok at wildlife. Don't forget to tune in next month for another awesome episode, and that's on Wildlife

Jess Avellino (17:38): You've Been listening to On Wildlife with Alex Re. On Wildlife provides general educational information on various topics as a public service, which should not be construed as professional financial, real estate tax, or legal advice. These are our personal opinions only. Please refer to our full disclaimer policy on our website for full details.