About Birds and their Adaptations to Climate Change

Birds are Changing Shape

Semipalmated sandpiper at JBWR (30550) A study in Ecology Letters from December 2019 has found that many migratory birds in North America are changing shape. The average body size of 49 out of 52 bird species examined from 1978 to 2016 dropped significantly. Also, in 40 species the average wingspan has increased significantly. Though, it is worth noting that there have been many studies that say the opposite. Bergmann’s rule states that species of animals in colder climates have larger bodies than those in warmer climates. Animals with larger bodies do not radiate as much heat proportinally as animals with smaller bodies because the ratio of surface area to mass is smaller. So, migratory birds are most likely losing mass to give off more heat from the climate warming. This comes with the possible negative consequence of birds not being able to store as much fat/energy for migrations.

The reason for increased wing length is unknown. Some say the longer wings help compensate for the decreased body mass. While some say the longer wings is not related with the decreased body mass.

Migration

Migration is moving from one place to another, typically a breeding range and wintering range. The breeding range is typically uninhabitable during the winter, so the animals move to the wintering range. The wintering range is more habitable, but the animals must compete with others for food and space. Migration helps with environmental uncertainty and leads to less competition for part of the year. However, the need for stopover sites lead to danger from habitat loss. An example of the dangers from habitat loss is the western sandpipers that stop at the mudflats close to the Fraser River estuary on the south coast of BC. The mud flats are covered with a layer of slime called biofilm. The sandpipers will eat this biofilm to prepare for the last part of their migration. Damage to these mudflats may cause permanent damage to the population western sandpipers.

Effects of Climate Change on Migration

Setophaga ruticilla Dobak

Birds are waiting longer to migrate and are migrating faster to combat the effects of climate change. Colder winters bring less available food. This means more time is needed to build up energy stores for migration. Also, some birds are waiting longer to migrate in the fall because of milder autumns. Others are migrating sooner in the spring because of spring starting earlier. With spring starting earlier in the breeding grounds, the birds have less time to take advantage of the abundance of food when they arrive. If the migration was delayed by 10 days, around 60% of this lost time could be made up by the faster migration, but the birds are always arriving too late to take advantage of the peak food abundance. Birds with longer lifespans won’t speed up their migrations as much because they have more time to pass on their genes. Overall, speeding up the migrations is causing a more than 6% mortality rate.

Many birds tell when to migrate off daylight hours. Although, with the effects of climate change, these birds are migrating at the wrong time because the seasons are starting at different times than they did historically. These birds may face weather that is too hot and may not be able build their nests fast enough. So, they will then try to raise their young really fast during the peak insect population. Others will migrate further north than usual because it is colder. Although, this more northern habitat may not be right for them and it comes with new dangers and competition. In the case of predators, they are moving further north into different habitats and hunting birds that have never come across them before. These birds will have minimal defences because they did not evolve to be around these predators. Birds can tell people about climate change by the ways they are changing their behaviour.

Corvids are Replanting Forests

Corvids are a group of birds consisting of crows, ravens, rooks, jays, magpies, treepies, choughs, jackdaws, and nutcrackers. Corvids have been known to "scatter hoard." They will gather seeds, fruit, and meat. Then hide them in many different locations and can remember up to 200 different locations. Although, they will always forget some of the food locations. Since the corvids like to hide food 1-2 inches under soil many of the seeds can start to grow. Some trees have even evolved to have more carbohydrates in their seeds, so the corvids will eat less of them, leaving more to be able to grow. The birds will even inspect the seeds to make sure they are not infested with insects, spiders, or fungi. This leads to the seeds most likely to grow being planted. Corvids will sometimes cache their food tens of kilometers away and prefer areas that have been damaged by fires. Corvids have helped move forests from places affected by climate change and replanted forests that have been destroyed. Some people have decided to put out seeds for jays to scatter around to replant forests, resulting in cheap labour.

Reintroducing the Hawaiian Crow Back into the Wild

Corvus hawaiiensis Most corvids are not endangered and are not as affected by human damages as some other animals. Many corvids are actually increasing in population size due to human impacts. This led to some concern over them raiding the nests of other species but, studies have shown that it isn't causing a big problem. However, not all corvids are safe from human impacts.

The hawaiian crow is currently considered extinct in the wild from introduction of new viruses and predators, and from hunting by humans. Captive breeding was originally inefficient because the males were forced to hang around the nests too much, causing aggression between the couple. Another issue encountered was that the egg shells were thin because of too much inbreeding. Eventually, these issues were worked out to have some success in increasing the population. Thirty hawaiian crows were reintroduced into the wild but only 5 survived and were brought back to captivity. Many were killed by the hawaiian hawk and other predators. The survivors were found to have anti-predator tactics. If these tactics are preserved they can be taught to the birds that stayed in captivity. Corvid fossils have been found on other islands where the hawaiian hawk does not live. So it has been suggested that releasing the birds on these islands might help them survive. The absence of these crows have caused damage to the environment because they were the main source of seed dispersal. Many of these plants can't create another generation because their seeds are not being planted.

Corvid Society

Most corvids are usually mates for life. The crows born in recent years will usually help their parents raise the current year's brood. Crows in different regions have different dialects. If a crow joins a new flock, it will learn the dialect from the dominant members of the flock. Young corvids have been observed playing games. Some games similar to "follow the leader," and "king of the hill" have been observed as well as playing with sticks and sliding down surfaces. This is believed to be important to their adaptive survivability. Studies have shown that ravens can tell the emotions of other ravens and possess empathy towards each other. Magpies have been known to hold funerals for their dead friends. They will lay grass wreaths and stand vigil for a while. Corvids do not usually migrate but they can undergo irruptive migrations. This may be in part why corvids are not suffering as much as other birds from climate change.

Other Bird Knowledge

Note: the rest of this webpage has nothing to do with climate change.

Random Corvid Facts

Pêga-rabuda, Eurasian Magpie (49045877246)

Feathers

The structure of feathers is as follows: The rachis is the shaft of the feather. The barbs branch off the rachis and branch into the barbules. The barbules have hooks on the ends called barbicels, which interlock with each other to hold the barbs together. The interlocked barbs form the vane of the feather. The quill is the pointy end of the feather that inserts into a follicle in the skin. Feathers are usually classified as a plumulaceous or a pennaceous/contour feather. Contour feathers are the vanned feathers that cover the body. The contour feathers grow in tracks in the skin and are not distributed uniformly over the body. The plumulaceous feathers are used for thermal insulation and are usually found under the contour feathers. Plumulaceous feathers don't have barcicels so the barbs move freely and can trap air. Feathers can be classified further into:

The weight of the feathers is usually 2-3 times the weight of the skeleton.

Colouration

Cyanocitta-cristata-004

The colour of feathers can be used as camouflage or as a way to attract mates. The feathers on the top of the bird and bottom of the bird can be different colours to provide camouflage when in flight. The colouring of feathers arises by pigments and/or structural colours. Feather pigments usually fall into the categories of carotenoids, melanins, and porphyrins.

Structural colours are produced by light being refracted off the structure of the feather. Iridescent feathers are made by light being split and reflected as some of its component colours. The colour of these feathers change with the viewing angle. With other feathers, air pockets in the structure of the feather can scatter light and produce a colour not dependent on viewer angle. This is how most blue colours are produced.

Flight

Bird plumage

Flight feathers are asymmetric feathers used for flight. They are usually larger and stiffer than other contour feathers. The flight feathers on the wings are called the remiges. The remiges are then categorized as primary and secondary feathers. The flight feathers on the tail are called rectrices.

*Despite the tertials being on the wing, they have nothing to do with flight. The tertials protect the remiges when the wings are folded.

Anting

Corvus Corone Alfred anting JdP 20190429 t190104

Anting is a behaviour seen in many birds that is mainly for feather maintenance. In active anting (the most common type) a bird places its wingtip on the ground. Working from the wingtip up, the bird will then take an ant and rub it on a feather. An ant will usually only be used once per feather and never more than three times. In Passive anting (less common) a bird rubs its wings and tail on an anthill to attract ants. The bird will then rub their head / beak through their feathers where the ants are to provoke them. The ants then will walk around the feathers freely.

The reason for anting is disputed/varies in different birds.

Citations

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