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Incubation

Snapping Turtles Laying Eggs – Sex Of Turtles Determined By Temperature

6-21-19 snapping turtle 1B0A1038It’s that time of year again, when female Snapping Turtles are leaving ponds, digging holes in sandy soil and depositing up to 80 eggs (20-30 is typical) before covering them up and returning to their ponds. While the sex of most snakes and lizards is determined by sex chromosomes at the time of fertilization, the sex of most turtles is determined by the environment after fertilization. In these reptiles, the temperature of the eggs during a certain period of development is the deciding factor in determining sex, and small changes in temperature can cause dramatic changes in the sex ratio.

Often, eggs incubated at low temperatures (72°F – 80°F) produce one sex, whereas eggs incubated at higher temperatures (86°F and above) produce the other. There is only a small range of temperatures that permits both males and females to hatch from the same brood of eggs. The eggs of the Snapping Turtle become female at either cool (72°F or lower) or hot (82°F or above) temperatures. Between these extremes, males predominate. (Developmental Biology by S. Gilbert)

If the cool temperatures we’ve experienced thus far this spring continue, there could be a lot of female Snapping Turtles climbing up out of the earth come September. (Thanks to Clyde Jenne and Jeffrey Hamelman for photo opportunity)

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American Crows Building Nests

3-6-19 A. crow IMG_1920Congratulations to Robyn Deveney and Chris Wings, the first Naturally Curious readers who accurately suggested the Mystery Photo depicted the tracks of an American Crow collecting nesting material. As I approached the pictured area, I flushed two black birds who were soon cawing and flying overhead, with a stick protruding from one of their beaks.

Crows are one of the earliest passerine, or perching, birds to engage in nest-building and egg-laying. Crows tend to build new nests each year, seldom reusing a nest from a previous year. In New England both members of a pair are busy collecting nesting material such as sticks, bark strips, weeds and mud, in March. They bring this material back to the nest site, which is typically a conifer, and construct a bulky nest usually in the crotch of the tree or on a horizontal branch. It takes anywhere from one to two weeks for crows to complete a nest and up to six days to lay 2 – 6 eggs. Incubation typically begins in early April.

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Barred Owl Chicks View The World For The First Time

6-4-15  barred owl chicks2  100 Barred Owl eggs (usually two or three) are often laid in a tree cavity, where the adult female incubates them for roughly a month. Fuzzy, white, downy chicks hatch and remain inside the tree for four or five weeks while being fed by both parents. When the young owls are two or three weeks old, their white down is replaced with gray-buff secondary down, and they gain the strength to climb up the inside of the tree and peer out at the outside world. In and out they go, perching on the rim of the nest hole for half an hour or so as they await the arrival of their next meal, and then retreating back to the safety and warmth of their nest. (Thanks to Alfred Balch, naturalist extraordinaire, for photo op.)

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Ospreys Laying Eggs

5-5-15 osprey 266Ospreys are late-season breeders compared to other raptors of their size, and are just starting to lay and incubate their eggs in the Northeast. This is thought to be an adaptive delay to allow ice to break up and to allow fish to move into shallow waters. (In years of late ice-out, ospreys may not breed.)

Both male and female ospreys incubate their 1 – 4 eggs, but the female generally does a majority of it, and nearly always is the incubator at night. The male typically brings the incubating female food, which she takes to a nearby perch to eat while he sits on the eggs. Once the eggs hatch (in about 5 weeks) the young are brooded by the female. The male does the fishing, bringing his prey back to the nest, eating his fill and then giving it to his mate to tear into small bits and feed to their nestlings.

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Common Loons: Egg-laying & Incubation

7-1-14  Loons #2 - incubating 404Typically Common Loons lay two eggs, each of which is roughly four inches long and olive green to brown in color, with brown or black splotches. The eggs are laid one to three days apart with the 28-day incubation period beginning when both eggs have been laid. Both parents incubate, turning the eggs when they switch places or during long periods of incubation. If the loon on the nest is anxious for relief, it will give a “wail” call, and if its mate does not respond, it continues wailing, even after leaving the nest to find its mate.

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