Wednesday, April 17, 2013

The Rookery

I cannot, I will not, disclose the location of this Great Blue Heron Rookery. My secret will keep them safe from disturbance, and help ensure their productivity.

 Perhaps you are fortunate to know of a rookery near you. Possibly, you've seen one and didn't know who the builders of these big nests were. Placed so high in the tree canopy, they look precarious from a distance.
Do they remind you of a Dr. Seuss landscape?

Great Blue Herons nest in colonies with other Great Blue Herons, or herons of other species.
Rookeries are found far from human settlements. They prefer this isolation and being away from disruptions. I photographed these from a distance of about 80 yards.

They nest in tall trees, usually at the top of vertical branches. Rookeries may be used for decades, and contain many nests. The one I observed contained about 20 nests, in various states of repair.

The nests are used over and over; and over the years become substantial in size. To accommodate these large birds, the nests are 2 - 3½ feet ( 61-106 cm) in diameter.

A few days after their initial spring arrival, herons begin to claim their nest sites and defend them against other heron pairs.

Sticks are gathered from the ground, from trees, and from old or even active nests. Sticks are 1 - 1½ feet (30-46 cm) long and about ½ inch (1.5 cm) in diameter.

Generally, the male brings in nesting material to the female, who greets him with a "stretch-display" (sticking her head vertically upward), then places his offerings in the nest.

It takes a few days to a few weeks to complete, with some nest-building continuing into incubation. Renovation of old nests is common, with finer twigs, leaves and grasses lining the inside.

During incubation, the incubating parent gets up, stands on the rim of the nest, and flies off for another food search, as its mate arrives. The arriving bird settles carefully over the eggs, occasionally turning them.

Eggs: 3-5, bluish green to pale olive, 1½" x  2½" (4cm x 6.5 cm) in diameter.

Incubation: 28 days, by male and female.

Nestling Phase: 7 - 8 weeks.

Fledgling Phase: 2 - 3 weeks. One brood per year.

I've changed my mind, and decided to tell you the location of these nests after all:
About 200 yards north of this southbound heron, and 50 - 70 feet above the ground.
A special thanks to Luke for permission to walk his land and photograph these gorgeous birds.
Great Blue Heron - Ardea herodias
Guide to Bird Behavior,  Volume Three -  Donald & Lillian Stokes  (Stokes)  © 1983