It’s officially spring! At least according to the calendar. Here in Boston, we just got finished with some cold, winter-like days. Which is not surprising because, you know, Boston in March is unpredictable like that.
But still! Warmer days are in the weather forecast and the spring flowers are starting to bloom! In honor of the coming spring, I want to introduce you all to a bird you’ve almost certainly seen if you live in the United States: the American robin (Turdus migratorius).
- Many birds are called robins
- The term “robin” isn’t actually that unique – dozens of bird species in different families (chats, flycatchers, thrushes) across the world have the word “robin” in their name. In fact, the American robin was named because early colonial settlers thought it looked similar to the European robin. We know today that American and European robins are unrelated. The American robin belongs to the thrush family, the same family that includes bluebirds. There are currently seven different subspecies of American robins that vary slightly in size and plumage.
- Keen eyesight
- Like many birds, American robins rely heavily on their eyesight. American robins have their eyes on the side of their heads, so they have monocular vision – each eye sees a different image.This comes into play when hunting for worms: they can see the tip of a worm poking out of the soil and small changes in the surface of the ground indicating a worm moving underneath. Further cocking their head to the ground and moving their head around lets American robins better gauge the depth of their environment and be accurate when attacking. In addition to their superb visual skills, American robins also have decent hearing. In fact, they seem to be able to hunt and find earthworms using sound cues alone.
- Worms and berries
- Have you ever seen an American robin hopping around in the grass? They were almost certainly looking for insects and worms to eat. While American robins have a flexible diet, it generally ends up being about 40% invertebrates and 60% fruits and berries. Worms tend to be the morning meal, with berries serving as dinner. American robins also tend to eat more invertebrates in the spring and summer, and transition to eating more berries and fruits in the fall and winter. You can even sometimes find drunk robins – they can get tipsy from eating honeysuckle berries exclusively or after feasting on fermented berries in the late winter and early spring.
- Not always a sign of spring
- Contrary to their cultural role as a harbinger of spring, not all American robins leave their breeding grounds in the winter to return in the spring. It is true, though, that we are much less likely to see American robins during the winter – they are spending the cold months roosting in trees and searching for food. The number of American robins that fly south for the winter depends on the local conditions such as temperature and food availability. It seems like they only go as far south as they need to in order to find food to last the winter. So that robin you saw on the first warm spring day may have been in your backyard for months.
- Multiple broods
- American robins are one of the first birds to begin laying eggs in the spring. You may have seen one of their nests: they are cup-shaped and made of grass, twigs, and feathers. American robin nests can be located on the ground or high in trees, but are typically found 5 to 15 feet above the ground in places with a firm support and protection from the rain. Think dense bushes, the crook of a tree, or window ledges. A clutch has between 3 and 5 eggs, and a pair of American robins typically has 2 or 3 broods of young each breeding season.
- Blue eggs
- Another classic feature of the American robin is their blue eggs. There’s a whole color named for it! (Hex code #96DED1 and CMYK value of 38, 0, 23, 0 for those who are curious). Their eggs are blue because of a bile pigment, biliverdin, that is deposited on the eggshell when they are being laid. Different concentrations of biliverdin lead to different blue shades on the eggshells, with smaller eggs and those laid first tend to be a more intense blue. But why are American robin eggs blue? Studies have found that bird eggs have to balance two issues: UV radiation from the sun and overheating. Darker eggshells are great at protecting the embryo from UV radiation, but at the cost of heating the egg more quickly and leading to sped-up embryonic development. American robins nest in areas with moderate light levels, so they don’t need to worry about overheating as much. Their eggshells focus instead on protecting the embryo from the sun’s radiation. Other birds that nest in bright environments tend to have light-colored eggshells to avoid the danger of over-heating.
- American robins are extremely flexible and have excelled at living in the suburbs of cities. However, we know that living near humans is also changing their behaviors. American robins typically sing at the crack of dawn; street lights and light pollution from bright lights is pushing their singing earlier and earlier. Their songs are also becoming more high-pitched so that they can be heard over the din of traffic.
I want to end with one quick note: as we head into spring, there’s a chance you will see baby animals around. Remember that in most cases, baby animals are just fine and have not been abandoned! Mother deer, for instance, will “cache” their fawns in a safe space as they go forage for themselves. Fledgling birds may look like they’re in trouble when you see them hopping around on the ground, but the parents are almost certainly watching and bringing them food. American robins, for instance, will leave the nest at 2 weeks old but remain near their parents on the ground, begging for food. They won’t actually fly away until 2 weeks later.
So if you see a baby animal, you should NOT mess with them (at least at first). Watch them for an hour or two to see if the parent comes back. If the baby still looks like it’s in trouble, you can then call a wildlife rehabilitation center for further directions. If you find a bird that has clearly recently hatched (eyes closed, few feathers), you can see if you can find the nest where it came from and gently put it back. Don’t worry, the parents will still take care of it after you touch it putting it back in the nest! But in general, baby animals are just fine, and if you’re really concerned, you should contact a professional.
I hope you all enjoy the singing birds that are starting up in your area!