Robins Breeding Habits
Robins Breeding Habits are very fascinating! I hope you are fortunate to have them nest nearby so that you can study them like I did! For several years, the Robins have built a nest in a wreath hanging on our porch. It is amazing how they care for their young! They lay their eggs mid morning because they eat a lot of earthworms when they are breeding. It was amazing watching them in action! Worms are most available before the sun is high. The robin will feast on worms before laying her eggs. A robin can then fly to her nest and lay her eggs easily! Most other birds need a long quiet period before they can lay eggs. They get a big breakfast later since they do not want worms!
Laying an Egg is Hard Work
Robins lay only one egg per day and it is hard work! They only have one ovary. The Ovary produces the eggs. The ovary of a bird looks like a tiny bunch of different-sized grapes. These “grapes” are the ova (which means the yolks).
One ovum that is ready to release looks gigantic. The others are only half this size, and several more are smaller. If there are others, they are tiny. Once a day, the largest yolk ovulates and pops off the ovary. From there, it travels down a tube, called the oviduct, to the outside of the robin’s body.
Egg Formation
If the female mated with a male, the yolk will become fertilized. If the robin has not mated, the yolk still goes down the oviduct. It will be a normal robin egg, but it will not become a robin. As the yolk goes down the oviduct, the walls of the tube drip watery proteins which is albumen and surrounds the yolk. Later on down the tube, there is a secretion of calcium components. This calcium becomes the eggshell. However, the egg remains soft until it is laid. The formation of the egg takes an extreme toll on the robin’s body!
Stops At Four
Robins normally lay four eggs and stop. However, they only lay one egg a day until their brood is complete. Some birds keep laying an egg a day if someone removes an egg. They can only stop when their brood feels just right.
On The Nest
Mother Robin lets all her eggs stay cool until she lays them all. This stops them from starting to develop. That ensures all babies hatch about the same time. Mother Robin lays all her eggs before she begins incubating them in the evening. Then she sits on the eggs for 12 to 14 days. a Mother Robin will rarely leave eggs for more than 5 or 10 minutes at a time, even in good weather. The female does most of the incubating, but the male has been known to take over for short periods.
Incubation
Mother Robin’s job is to keep the eggs warm at the proper temperature. She must keep the eggs warm during cold weather and shade them if the weather gets hot. She must rotate the eggs a few times every day.
If you ever watched a robin, you see her hop on the rim of the nest and uses her bill to gently turn the eggs. That practice keeps all the eggs at the proper temperature and keeps the babies from sticking to the insides of the eggshells. Males will sit on the eggs once in a while, but they do stay around all day and watch over his family. If Mother calls for help or is in distress he comes to her aid. Her mate will bring her food but she can also leave and feed herself!
Sharing Her Body Heat
Robin eggs must keep warm to develop. Mother Robin has a body temp of 104 degrees F. or even warmer. The Robin’s feathers insulate and keep the bird’s body heat inside. Outer feathers still feel cool when touched. Female Robins must keep their eggs warm! A Brood Patch on their bellies is where their feathers fall out. Mother Robin projects body heat by parting her outer feathers and pressing her bare hot tummy on her eggs or babies. Hidden by outer feathers is the brood patch and covers the bare area. (The same principle as closing the oven door so the heat stays inside.) When Scientists band a female robin, they blow the tummy feathers to look for a hidden brood patch!
Brood Patches contain receptors that let the Mother Robin sense the egg temperature! Mother Robin changes her incubation time according to her temperature sensing! She might sit more or less tightly on the eggs! She might even leave the eggs exposed during the time she leaves to feed or drink!
Hatching Out
A Chick has a difficult time struggling its way out of the egg. It breaks a hole in the shell with a hard hook on its beak, called the egg tooth. Then it must struggle with everything it has, in between rest periods, to get out. This is why hatching can take a full day. Normally the eggs hatch a day apart in the same order. Naked, reddish, wet, and blind, the babies need an abundance of food. Both parents have a full-time job finding food to feed the constantly hungry babies for the 9-16 days in the nest.
New fledged robins will mostly take cover on the ground once they leave the nest. They need at least two weeks before they are capable of flight. At this time, they follow after their parents and beg them for food. Afterwards they still stay near the nest for about four months.
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