As we enter June, we are at the height of the nesting season for most of our local avifauna. And this means that once again the world will be full of baby birds.

Before going any further, I have to repeat the perennial reminder that all birders give to everyone who will listen at this time of year:  Leave the baby birds alone!

When you see young birds out of the nest, you should not do anything with them other than maybe move them a short distance to a place of shelter away from immediate danger.

To understand why this is, let’s talk about baby birds and the different varieties in which they come.

There are in general two different types of baby birds. These are called precocial and altricial. You may not be familiar with these terms, but you are certainly familiar with the difference between the two.

Precocial young come out of the egg covered with thick fluffy down, able to walk or swim, see and feed themselves. They still need their parents around for protection, warmth and to help them learn their way in the world. But they are not completely dependent on the adults for survival. Precocial young usually leave the nest within hours of hatching, as soon as their down has dried.

Freshly hatched turkeys, chickens, ducks and geese are well-known examples of precocial young. They are also found in many other water birds and shorebirds, like Killdeer and woodcock. All domesticated avian livestock have precocial young, as these can be reared easily by people without any bird parents around.

Altricial young, also called dependent young, are very different. They come out of the egg blind, weak, mostly naked and utterly dependent on their parents for everything. They usually stay in the nest for several weeks while their parents tend to their every need, keeping them fed, warm and clean.

Altricial young birds go through several stages of life. First is the helpless nestling stage. A nestling is a fragile creature and may die within hours in the absence of its parents. They must be fed high-energy food dozens of times a day. Their waste must likewise be removed from the nest as soon as it is produced. Conveniently, their waste comes out in tidy little sacs that the parents carry away. Nestlings have fast metabolism and almost no insulating down or feathers, so they must also be constantly protected from chills and damp. This likely sounds familiar to most of you, as human newborns are also altricial young, quite similar to nestling birds in their needs (but without the tidy waste sacs).

Healthy nestlings grow with amazing speed. Soon their eyes open and they begin to acquire feathers. Within a few weeks they reach the point where they have outgrown the nest, and they leave it. The act of leaving the nest is called fledging, and recently fledged birds are called fledglings.

Even though they have left the nest, fledglings are not yet fully grown. They are smaller than adults, with short wings and only partial flight feathers. They can only flutter around for short distances. But, and this is the key point, they are still being fed and protected by their parents. The parents keep track of the young by their voices and continue to feed them for anywhere from a week to several months more after fledging.

If you listen carefully for the high-pitched begging calls of fledgling birds, you may be able to spot them. Sometimes you will see an entire brood lined up along a branch, impatiently awaiting their turn to get the morsel their parent is bringing.

Soon enough, the fledglings reach full size. Unlike mammals, most birds grow to full adult size within only a month or two of hatching. This is true even for the big birds. Once they reach full size and have full flight feathers, their parents abandon them. The young are resistant to this, and will often continue to beg and pester their parents after they have lost interest.

An interesting point here is that all these parental care behaviors are hard-wired into the parents’ brains as instincts and regulated by the time of year and their seasonally shifting hormones. When an adult bird has young, the urge for it to stuff food down a gaping, begging, nestling mouth is literally irresistible. If parents lose their own nest, they will sometimes begin feeding other nestlings that are not their own. They will even feed babies of completely different species to satisfy the intense parental instinct.

Once the young are fully grown and the correct amount of time has passed, these instincts switch off. Suddenly, that begging fledgling becomes just an annoying, grown-up bird, trying to steal the parents’ food. The fledglings’ instinct to beg fades away too, and the young start to feed themselves and set out on their own.

These fully grown young of the year are called juveniles. Though they are as big as adults, juveniles often still look different from their parents. For example, juvenile towhees are brown and streaky, unlike the crisp patterns of the adults. Juvenile robins have speckled breasts. By the end of summer, most of the birds you will see in the wild are juveniles hatched and raised in just the previous few months.

So now it should be clear why you should leave baby birds alone. Precocial young are just fine. They may look scared and lost, but more likely they are just afraid because some huge, featherless monster is approaching them. And if mamma is a big goose and is nearby, you might just find yourself on the receiving end of a beating from her!

Altricial nestlings do sometimes fall from the nest prematurely. But sometimes they are also pushed from the nest for being weak or diseased. Regardless, hand-rearing a nestling of a wild bird is difficult even for professionals. If you take it home, it will die. If you know where the nest is, and you can reach it, you can place the nestling gently back in the nest. But you risk damaging the nest and putting the other nestlings in danger.

Recent fledglings are often found and misunderstood as having “fallen” from the nest. They did not fall, they jumped, and it was the proper time for them to make the leap. Their parents are nearby, probably scolding you. If the fledgling is in a dangerous place, you can try to herd or carry it somewhere safe. No, the parents will not “smell” you on the baby if you pick it up. Birds have no sense of smell. But if you try to return a fledgling to the nest, you will more likely just chase all the remaining babies out of the nest, and now you have an entire brood fluttering around your yard!

Taking a baby bird in with the thoughts of caring for it yourself is almost always a death sentence for it. Leaving them in the wild where you found them actually gives them better chances. Birds have been raising babies in the wild since the age of dinosaurs. They do not need our help.