Spotted Sandpiper Chicks - Actitis macularia
Spotted Sandpipers incubate eggs for 20 to 25 days and finding at least two and perhaps three families with one or more chicks in the last week, which is only five weeks after the flood, surprised me.
The first four photos are from July 25 and are from a family with at least two chicks. I knew a nest or chicks were close based on the display of the adult. The adult flushed from some low willow brushes about 5 to 10 meters inland from the Elbow River.
Willow bushes survived fairly well in the raging flood waters, which implies they have tenacious roots. Lower brushes up to one meter look normal. Higher brushes over two meters are alive but bent over. The brushes in this location were all less than a meter high.
As I carefully advanced, two chicks suddenly scattered in different directions. I kept a close eye on one chick and this eventually allowed the following photos.
Several days earlier I saw another solitary chick in a different location but I turned my gaze away for a few seconds to raise my camera, and the chick was long gone. These chicks can run very fast through the underbrush. Keeping my eye on the photographed chick was quite a challenge in the underbrush and the photos were only possible when the chick fortuitously turned towards the water. The shoreline had much less cover.
Once out of the underbrush, this chick scurried straight for the water, and without a moments hesitation, swam away from shore. There was only a modest current because the water was separated by a land bar from the main flow of the river, and I suspect the family was in this location by deliberate choice. A shoreline with willow underbrush adjacent to water with a modest current is likely an ideal location for food, security, and water training.
I walked away from the area and stood and watched. The chick swam around for perhaps a minute and then swam back to shore and headed towards the original area where I saw the adult and chicks.
The picture above and the following three photographs are from July 27 and show a solitary and older chick from a different location about a kilometer away.
This chick is larger, has browner tones, and the feet are much larger and yellowish-red. I suspect this chick is at about one week older. The chicks leave the nest as soon as the down is dry and are able to fly by 16 to 18 days. Neither of the chicks in the photographs have flight capability and are therefore less than this age. Remarkable growth and development over the first few weeks of life!
Presuming the first chick is about 3 days of age and the second chick is 10 days of age, and adding the incubation of 20 to 25 days, implies the eggs were laid for the first chick 23 to 28 days ago and 30 to 35 days ago. Since the flood was 35 days prior to the first photographs, this implies the eggs were laid after the flood. This makes sense, because the flood-waters likely destroyed the existing nests and eggs, which are typically on the ground and within 20 to 30 meters of shore.
When I originally did the math after seeing a solitary chick on July 24, I presumed the mother was "fortuitously pregnant" at the time of the flood and had not laid the final egg of a typical 4-egg clutch on June 20th (Flood Day) and laid the egg on higher ground the next day. Finding two families and therefore two "fortuitously pregnant" mothers in the small area where I hike suggested I needed to do some more thinking and research.
Spotted Sandpiper females are polyandrous. They might mate with more than one male in a season. If so, the male of the first clutch takes care of the eggs. Males are reported to have higher prolactin levels than usual and this fits with more post-hatch nestling care behaviour. Females are reported to have higher testosterone levels than usual and this fits with observations of courtship and nesting behaviour.
Females are reported to "store" sperm for up to a month. At the time of the flood all female Spotted Sandpipers likely had "stored" sperm. Spotted Sandpipers are usually single brooded, polyandrous behaviour notwithstanding. Faced with the loss of the first brood to the flood-waters, perhaps the females, inherently driven to breed each year, promptly fertilized one or more eggs with the "stored sperm" and expedited a clutch with only one or two eggs. This would explain why there are so many Spotted Sandpiper chicks in a limited geographic area so soon after the flood.
References
The Atlas of Breeding Birds of Alberta. Federation of Alberta Naturalists. 2007.
Baicich PJ, Harrison CJO. Nests, Eggs, and Nestlings of North American Birds. Princeton UP. 2005.
Beadle D, Rising J. Sparrows of the United States and Canada. Princeton UP. 2003.
Cornell University eBird. http://www.allaboutbirds.org/guide/spotted_sandpiper/lifehistory. 2013.
Fisher C, Acorn J. Birds of Alberta. Lone Pine Publishing. Edmonton. 1998.
Sibley David A. The Sibley Guide to Bird Life and Behavior. Alfred A Knopf, Inc. New York. 2001.
Spotted Sandpipers incubate eggs for 20 to 25 days and finding at least two and perhaps three families with one or more chicks in the last week, which is only five weeks after the flood, surprised me.
Willow bushes survived fairly well in the raging flood waters, which implies they have tenacious roots. Lower brushes up to one meter look normal. Higher brushes over two meters are alive but bent over. The brushes in this location were all less than a meter high.
As I carefully advanced, two chicks suddenly scattered in different directions. I kept a close eye on one chick and this eventually allowed the following photos.
When I originally did the math after seeing a solitary chick on July 24, I presumed the mother was "fortuitously pregnant" at the time of the flood and had not laid the final egg of a typical 4-egg clutch on June 20th (Flood Day) and laid the egg on higher ground the next day. Finding two families and therefore two "fortuitously pregnant" mothers in the small area where I hike suggested I needed to do some more thinking and research.
Spotted Sandpiper females are polyandrous. They might mate with more than one male in a season. If so, the male of the first clutch takes care of the eggs. Males are reported to have higher prolactin levels than usual and this fits with more post-hatch nestling care behaviour. Females are reported to have higher testosterone levels than usual and this fits with observations of courtship and nesting behaviour.
Females are reported to "store" sperm for up to a month. At the time of the flood all female Spotted Sandpipers likely had "stored" sperm. Spotted Sandpipers are usually single brooded, polyandrous behaviour notwithstanding. Faced with the loss of the first brood to the flood-waters, perhaps the females, inherently driven to breed each year, promptly fertilized one or more eggs with the "stored sperm" and expedited a clutch with only one or two eggs. This would explain why there are so many Spotted Sandpiper chicks in a limited geographic area so soon after the flood.
References
The Atlas of Breeding Birds of Alberta. Federation of Alberta Naturalists. 2007.
Baicich PJ, Harrison CJO. Nests, Eggs, and Nestlings of North American Birds. Princeton UP. 2005.
Beadle D, Rising J. Sparrows of the United States and Canada. Princeton UP. 2003.
Cornell University eBird. http://www.allaboutbirds.org/guide/spotted_sandpiper/lifehistory. 2013.
Fisher C, Acorn J. Birds of Alberta. Lone Pine Publishing. Edmonton. 1998.
Sibley David A. The Sibley Guide to Bird Life and Behavior. Alfred A Knopf, Inc. New York. 2001.
No comments:
Post a Comment