Why do birds only lay a few eggs?

Answer 1

Eagles are large birds and their young when they hatch out of eggs are pretty big when compared to the young of other birds. Caring for too many kids (Esp with the amount of food they eat) may get difficult for the eagle parents which will bring down the chances of their survival. Hence 1-3 eggs in one brood is easier to manage and make sure the kids survive.

This may be the reason why evolution ensured that eagles have only around 3 eggs per lot.

Answer 2

Birds are limited in the number of eggs they can lay by the fact that each egg must spend a full twenty hours in the female's single oviduct (on the left side) after being fertilised.

This anatomical characteristic basically means birds must lay a few eggs and expend a great deal of energy to ensure as many become capable of foraging effectively. In many species outside the Enriched World, "helpers" are present to aid the acquisition of scarce food, whilst in species feeding on easily found food like fruit, it is not uncommon for males to take no part in the rearing on young. In some species, males and females take turn incubating and feeding the egg(s) and chick(s), whilst in others either the male or female will stay at the nest while the other sex goes off to find food.

The opposite of this strategy would be to lay many eggs and spend less energy caring for them; the drawback of this is that many eggs would not survive though, so it is more beneficial for birds to lay fewer eggs and have more of them survive.

Answer 3

Birds lay so few eggs essentially because, with the exception of self-feeding precocial species, they have to feed their young for a substantial period. Except in the young "Enriched World" of Eurasia, North America, New Zealand and southern South America, where food is easy to find and highly nutritious, this care is very costly since successful foraging takes a long time to learn. In extreme cases, breeders of some species must have "helpers at the nest" to rear any chick whatsoever, as with the White-Winged Chough, Apostlebird or Varied Sittella.

In the "Enriched World", where food is more abundant but highly seasonal and absent during winter, parental care can be greatly reduced - compare the 70-day post-fledging period of the Varied Sittella with the 7-day period of similar-sized birds in Europe!

Answer 4

Eagles lay their eggs in trees so any other animal may not eat it or humans may not step on it
Pairs usually start a new nest in a living tree, though there are often dead trees ("snags") nearby where they have a view all around when they're resting near the nest. The healthier the tree, the better. Eagles use and keep adding sticks to their nests for years and years. One well-studied Ohio nest was used for 34 years, until the tree finally blew down. Sometimes a tree with an eagle nest dies after many years. If the tree remains standing, the eagles often remain there as long as their nest is secure. But the healthier the tree is to start with, the longer it will last.

source

http://www.learner.org/jnorth/tm/eagle/NestAbout1.html

Answer 5

Breeding season for eagles varies according to the region, and the species of eagle.

For example, bald eagles in the south lay their eggs in Autumn - anytime from late September through to November, while in the Great Plains and Mountain West, breeding season may be in late winter and early Spring - January through to March. Breeding season in Alaska is also in Spring - late March to early April. In some areas of North America, bald eagles lay their eggs at around May, in late spring.

By contrast, the wedge-tailed eagle of Australia breeds anytime from mid-Autumn to early Spring, though most commonly they lay their rggs in July (mid-Winter).

Answer 6

because it is smaller