Overview of a Birds Nesting Cycle from NestWatch/Cornell Lab of Ornithology

More than 700 bird species breed in North America, and the variations in their behaviors are fascinating and complex. Different species find mates, build nests, lay eggs, and raise their young in different ways…

1. Finding a place to breed

Throughout the year, day length is the cue that tells most birds what season it is, triggering physiological changes, such as the readiness to migrate or to breed. Most birds, especially those in temperate regions, must time theirbreeding activities so they will be feeding their nestlings when food is most abundant.

2.Choosing a Mate

While territories are being claimed, males and females also try to attract mates.Males often try to advertise their ability and their vigor by exhibiting bright breeding plumage and by singing, drumming, or calling.

Well before nestlings arrive, however, birds need to select a breeding territory. Most bird species form a pair bond with the male and female staying together throughout the breeding season. It was once thought that nearly 90 percent of all birds were monogamous, but new evidence using DNA profiling has revealed that strict monogamy is not so common. Many birds may have a single social mate who helps raise the young, but they may actually have mated with additional partners. DNA analysis shows that even birds that presumably “mate for life,” such as bluebirds and Bald Eagles, may not always be faithful. The young in one nest actually may have been fathered by different males!

Some birds are polygamous, forming social bonds with more than one bird of the opposite sex. Sometimes males have more than one mate at the same time (polygyny). Less commonly, females may have social bonds with more than one male (polyandry).

In most bird species, the female chooses her mate. This is one reason whymales are often the “showier” or more colorful sex. Besides physical appearance, females also may assess factors such as nest site quality and the male’s ability to provide food resources, vocal behavior, age, and courtship displays.

Well before nestlings arrive, however, birds need to select a breeding territory.Resident species may keep a territory throughout the winter or look for a new one in spring. Migratory birds begin looking for and defending a territory or nest site as soon as they arrive in spring. Good territories provide nest sites, reliable food sources, and protection from predators.

3.Nest building

Nest provide a safe place for the eggs and young. Bird nests are extremely diverse, although each species typically has a characteristic nest style. Some birds do not make a nest and simply lay eggs in a scrape in the ground or other substrate. Other birds may make nests from natural materials such as grasses, leaves, mud, lichen, fur, and dung, or manmade materials such as paper, plastic, trash, yarn, and even barbed wire! Nests can be found almost anywhere—on the ground, in trees, in burrows, on the sides of cliffs, in and or on manmade structures, etc. Females typically build the nest, but sometimes both parents or just the male will build it.

4.Copulation and Egg Formation

During the breeding season, hormonal changes cause the internal testes of males to swell to more than 1000 times their normal size, and the ovaries and oviduct of females to increase in size in preparation for egg fertilization and egg development. During copulation, the male’s cloaca contacts and ejects sperm into the cloaca of the female. This is sometimes referred to as the “cloacal kiss.” The sperm travel to the oviduct where they can be stored for long periods in sperm storage tubules. If all goes well, the sperm penetrate through the wall of the ovum (egg) and fertilization takes place. During the first stage of embryonic development, known as the blastocyst stage, the egg shell develops. Ovulation and laying take about 24 hours, so females produce at most a single egg per day.

5.Egg Laying and Incubation

The number of eggs a female lays in one nesting attempt (also known as clutch size) varies widely depending on the species. For example, many tropical birds have clutches of only two or three eggs. Waterfowl such as Wood Ducks can lay up to 15 eggs in one nesting attempt. Clutch size can also vary widely within a species depending on food and calcium availability, latitude, age of female,seasonal timing, weather, and time of year. The size, shape, color, and texture of bird eggs are also extremely variable.

Birds incubate their eggs to keep them at the proper temperature to ensurenormal development. Female songbirds usually begin incubation after they have finished laying all the eggs so that they will hatch at approximately the same time. Other birds, such as herons, cranes, cormorants, and raptors(eagles, hawks, and owls) begin incubating as soon as the first egg is laid, and the eggs may hatch on different days. In some species both the male and female may incubate eggs. Incubation time varies depending on the species, buttypically, the larger the bird, the longer the incubation period.

6.Hatching

Songbirds and most sea-birds have altricial young—the newly hatched birds are blind, naked, and helpless. They remain in the nest where the parent can feed them and brood them, sitting on them to keep them warm. Immediately after hatching, altricial birds can do little more than open their mouths to beg for food. Their mouths are often very bright and patterned. For a long time, scientists thought this helped guide parents to place food; it may also provide information on chick identity, health, and quality.

Unlike altricial birds, precocial birds such as ducks and many shorebirds are born fully feathered, mobile, and with eyes open. Incubation periods arelonger for precocial birds than altricial birds, allowing for increased embryonic development in the egg, and therefore they have enhanced motor and sensory functions at hatching. Precocial young are much more independent after hatching, but in most cases need several more weeks before they can fly.

7.Feeding and Raising Young

For the first week of life, most altricial birds cannot control their own body temperature—similar to reptiles and other cold-blooded animals—and must be constantly brooded (kept warm) by the parents. Usually, by the end of the first week, their eyes are open and their feathers are beginning to emerge. During these first 10 days, nestlings experience remarkable growth—some are able todouble their body weight several times!

To keep up with demand, parents must supply food for themselves and their young. This is an extremely dangerous time for the parents who are constantlyforaging for food, and for the young, whose noisy cries for food may attract predators. After two to three weeks, most songbirds are usually ready to leavethe nest. Other birds, such as birds of prey, may stay in the nest for as long as8 to 10 weeks.

In contrast, precocial birds such as ducks and many shorebirds spend hardly any time in the nest and are often seen wandering in search of food alongside their parents hours after hatching. Most precocial birds gain the ability to flywithin a few weeks to a few months after hatching.

8.Leaving the Nest

After leaving the nest, or fledging, the young birds typically remain close to parents for a short period of time. During this time, young birds must learn to survive on their own and are very vulnerable to predators and starvation. Most birds nest only once per year, but some species can nest up to four or even five times in one breeding season.

Friends of the Edmonds Marsh Meeting, Thursday, April 8th, 7:30 PM, Frances Anderson Center

At the Frances Anderson Center Room 302

700 Main Street Edmonds

• Come and learn about the Marsh and the history of this important estuary
• Join us as we identify and study the issues and problems facing the viability of the Marsh
• Together we can seek solutions to preserve this valuable resource

The Marsh needs friends and support from our community

Friends of the Edmonds Marsh

Mission Statement: To expand and restore functional estuarine habitat within Edmonds Marsh and protect the remaining wildlife habitat by engaging the community to preserve, steward and enjoy our most natural asset.

Contact 425-771-8165 or Susie.Schaefer@pilchuckaudubon.org for information

April 7th, Frogwatch starts at the Frances Anderson Ctr, Edmonds, for four weeks, Wed. evenings, 7PM

5 REASONS TO STOP TOPPING TREES By Cass Turnbull

What’s wrong with topping?

The misguided practice of tree topping (also referred to as stubbing, dehorning, pollarding, heading, and by several other euphemisms) has risen to crisis proportions nationally over the last decade.  Topping has become the urban forest’s major threat, dramatically shortening the lifespan of trees and creating hazardous trees in high-traffic areas.

The importance of trees to the urban and global ecology is only now becoming fully known and appreciated.  This dawning has not yet been accompanied by adequate public education and sound public policy to ensure tree survival and our own safety.

DON’T TURN YOUR VALUABLE COMMUNITY ASSETS INTO LEGAL, AESTHETIC AND ECONOMIC LIABILITIES! PLEASE READ AND CONSIDER THE FOLLOWING.

1.  IT WON’T WORK.

Topping won’t work to keep trees small.  After a deciduous tree is topped, its growth rate increases.  It grows back rapidly in an attempt to replace its missing leaf area.  It needs all of its leaves so that it can manufacture food for the trunk and roots.  It won’t slow down until it reaches about the same size it was before it was topped.  It takes at maximum a few years before your tree returns to near its original size.

An exception to the grow-back-to-size rule comes if you damage a tree’s health so it hasn’t the strength to re-establish itself.  It is, in effect, dying and will continue on a downward spiral for years.  Topping can’t make a significant size difference-not for long.  The species or type of tree you have determines its size.  A dogwood or Japanese maple may grow from 10 to 30 feet in its life, an oak or an ash from 10 to 90 feet.  You can’t “stop” trees with topping.  If you succeed, you have killed them.

2.  IT’S EXPENSIVE.

A topped tree must be done and re-done every few years-and eventually must be removed when it it dies or the owner gives up.  Each time a branch is cut, numerous long, skinny young shoots (called suckers or watersprouts) grow rapidly back to replace it.  They must be cut and recut, but they always regrow the next year making the job exponentially more difficult.  Much like the many-headed Hydra snake that Hercules battled, people create maintenence monsters in their back yards.  A properly pruned tree stays “done” longer, since the work does not stimulate an upsurge of regrowth.  Proper pruning actually improves the health and beauty of a tree, costing you less in the long run.

Topping also reduces the appraised value of your tree.  A tree, like any landscape amenity, adds to the value of your property.  Appraisers subtract hundreds of dollars from the value of a tree when it’s been topped (using the International Society of Arboriculture’s guidelines for evaluation).  You can even sue a tree company for wrongfully topping a tree.

3.  IT’S UGLY.

The sight of a topped tree is offensive to many people.  The freshly sawed-off tree limbs are reminiscent of arm or leg amputations.  And the freshly-sawed look is just the beginning of the eyesore; the worst is yet to come, as the tree regrows a witch’s broom of ugly, straight suckers and sprouts.

The natural beauty of the tree’s crown is a function of the uninterrupted taper from the trunk to ever finer and more delicate branches, and the regular division of the branches.  Arborists consider the topping of some trees a criminal act, since a tree’s 90-year achievement of natural beauty can be destroyed in a couple of hours.

Topping destroys the winter silhouette of a tree.  The regrowth of suckers or shoots will bloom poorly, if at all.  Some trees will reestablish themselves after many years-but by then they will be the same size as before. Many topped trees are considered a total loss.

4.  IT’S DANGEROUS.

opping creates a hazardous tree in four ways:

• IT ROTS.  Topping opens the tree up to an invasion of rotting organisms.  A tree can defend itself from rot when side branches are removed, but it has a hard time walling off the pervasive rot to which a topping cut subjects it.  Rotted individual limbs-or the entire tree-may fail as a result, often years later.
• IT STARVES.  Very simply, a tree’s leaves manufacture its food.  Repeated removal of the tree’s leaves-its food source-literally starves the tree.  This makes it susceptible to secondary diseases such as root rot—a common cause of failing trees.
• WEAK LIMBS.  New limbs made from the sucker or shoot regrowth are weakly attached and break easily in wind or snow storms-even many years later when they are large and heavy.  A regrown limb never has the structural integrity of the original.
• INCREASED WIND RESISTANCE.  The thick regrowth of suckers or sprouts resulting from topping make the tree top-heavy and more likely to catch the wind.  This increases the chance of blow-down in a storm.  Selectively-thinned trees allow the wind to pass through the branches. It’s called “taking the sail out” of a tree.

5.  MAKES YOU LOOK BAD.

Topping makes you appear to be a cruel or foolish person.  Your friends know you better.  But the more your neighbors come to understand topping for what it is, the lower you will fall in their esteem.  You may top a tree to create a water view, but you should know that you have some friends and neighbors-who probably won’t say so because they are being tactful-who see a view of a butchered tree with water in the background.

Join us at the Frances Anderson Center, Edmonds on 3-25, for Native Plant Gardening Talk, 7:30-8:30PM