| 
| | | 
The Birds: The Heronry of the Martin Griffin Preserve
The birds are nesting!
To the delight of visitors, volunteers and staff, on April 6th Great Egrets returned to the historic heronry at ACR's Martin Griffin Preserve. Within days, our science staff confirmed that pair bonding and nest building had begun. This page is updated weekly during the nesting season. These are preliminary numbers based on the most recent observations of the colony.
From ACR science staff on June 1, 2013
17 active Great Egret nests and one Great Blue Heron nest.
| Great Egrets (GREG) | Great Blue Herons (GBHE) | |
| Total Nests | 17 | 1 |
| Stage unknown | 1 | |
| Stage 1 | 16 | 1 |
| Stage 2 | ||
| Stage 3 | ||
| Stage 4 | ||
| Eggs | ||
| Chicks |
|
Stage |
Description |
Timing |
|
1 |
Egg laying, incubation, adult lying down for long periods, egg turning, nest relief of one parent by another |
Lasts approximately 28 days. |
|
2 |
Hatching (small downy chicks), feeding low in the nest, need to watch carefully when the adults move |
Approximately one week (or slightly less) |
|
3 |
Chicks are usually standing, most/all of the down is replaced by juvenile plumage, parents continue to stay at nest |
7 days – 3.5-4 weeks |
|
4 |
Adults are not continuously at nest (May remain after feeding), chicks usually on nest platform, |
3.5 weeks – 4 weeks, up to 8-12 weeks |
|
5 |
Young often off nests |
8-12 weeks |
The History
The Martin Griffin Preserve is home to one of the most significant and well-studied Great Blue Heron, Great Egret and Snowy Egret nesting sites on the West Coast. As they have for generations, Great Egrets still return annually in early spring to resume their mating rituals, nest building and egg laying. In the summer, new chicks can be observed raucously begging for food and testing out their wing feathers during first flights. By mid summer - usually sometime in August - all chicks will have fledged the heronry.
Where are the Great Blue Herons?
While Great Blue Herons and Snowy Egrets have historically nested in the Picher Canyon colony, their numbers have declined over the past several years. For the last two years, Great Blue Herons have also been nesting across the lagoon on the Bolinas mainland and Kent Island, and ACR science staff is monitoring their nests.
For visiting information, click here.
