Wednesday, February 20, 2013

Canada Geese at EagleCrest

Check out the video:
The Canada Geese laid their first egg at Eaglecrest on February 19th between 5:05pm and 6:18pm PST. Mother goose Wilma won't begin full incubation until most of her eggs are laid, which helps assure that the young goslings are all at about the same stage of development. I don't want to guess at a hatching date right now, but this is roughly what nesting looked like last year:
  • 1st egg: February 26
  • 2nd egg: February 28
  • 3rd egg: March 1
  • 4th egg: March 4
  • 7th and last egg: March 10
  • Hatching: April 6th
  • Nest Leave Taking: April 7th 
If the geese follow the same pattern this year, we should see an egg roughly every two days, with full incubation beginning about the time the last egg is laid. Hatch should start 24-28 days later: last year took 27 days. The goslings will jump from the nest within about 24 hours of hatch. We'll be able to watch the family swimming in the pond, but they will not come back to the nest once they've left it. 

People expressed a lot of concern about these three things last year: 
  1. Mother goose isn't spending enough time on her eggs
  2. The goslings will starve when they hatch
  3. The goslings will die when they jump from the nest
So let's talk about them, shall we? 

Incubating the Eggs
Mother goose won't begin full incubation until around the time her last egg is laid. Embryonic growth and development is a fast-paced chemical process that requires heat. By delaying incubation, mother goose delays the onset of embryonic development  and assures the synchronous hatching of fertilized eggs. Synchronous (closely-timed) hatching is especially important in the case of Canada geese and similar birds, which leave the nest roughly 24 hours after hatching. Unhatched eggs or birds too young to follow their parents die. 

I used to think that eggs would die if birds stopped sitting on them for even brief periods of time. Not true! Embryos are less sensitive to cold than to heat, particularly before incubation has started, and few birds incubate continuously. Wilma will regulate the temperature of her eggs by varying the amount of time she sits on them, and the tightness of her sit. If the weather is warm and sunny, she may spend a great deal of time off the eggs. We also might see her cover the eggs with soft nesting material.

Feeding the Goslings
I'm going to drop some words on you readers. Canada geese are precocial - that is, the young are relatively mature and mobile from the moment they hatch. They are born with their eyes open and can swim, run, and jump shortly after leaving the egg. This is important, since precocial species are normally nidifugous, meaning they leave the nest shortly after birth or hatching. 

Just before hatching, the goslings will consume whatever yolk and albumen remains in their eggs. This provides enough food energy for the next 24 to 48 hours. Once they've jumped from the nest, their parents will lead them to water and protect them from predators. Wilma and Fred do not need to provide food in the nest, and the goslings will find food (mostly) on their own once they reach the water. 

Roughly 24 hours after hatching, Wilma will leave the nest and the goslings will jump after her. While this seems scary, it is very normal for geese. Canada geese have been documented nesting on heron nests, osprey nests, cliffs, and man made structures. Nesting in high places helps protect eggs and very young babies from ground-bound predators including raccoon, coyotes, opossums, cats, and dogs.

The jump is over very quickly. Dad Fred will be waiting on the ground below to help protect his family. Wilma will fly down from the nest and honk for the goslings, who will quickly follow her out of the nest. Their  light weight and downy bodies will help protect them from injuries when they land on the soft grassy surface below the nest, and Eaglecrest staffer Ramblin' Raptor will also put out straw or grass to help cushion their landing. Once the goslings have landed, their parents will lead them directly to the pond, honking and hissing all the way.

To see just how fast the jump goes, watch this video from 2012:

I've often heard Bob say that birds wouldn't do it if it didn't work. Successful behaviors lead to more offspring to pass those traits on to. Geese that are good at synchronous incubation will have better offspring survival rates than those that aren't. Geese that nest high will lose fewer eggs and young to ground-based predators, offsetting potential losses caused by landing injuries. Whatever we might think as human watchers, Fred and Wilma are following a way of life that has produced more winners than loosers. Mama (goose) knows best.

1 comment:

Bonnie said...

This is so totally amazing. Thank you.