The Flight of the Snow Geese

 

Snow Geese (Anser caerulescens) rising with the sun
at Bosque del Apache National Wildlife Refuge, New Mexico.

One of the world's great wildlife spectacles takes place each winter along the Rio Grande in New Mexico. Over 50,000 Snow Geese (Anser caerulescens) that breed in the North American Arctic during the summer, spend the cold months on the ponds and fields along the river.  

Sunrise over the Bosque del Apache
National Wildlife Refuge, New Mexico. 

Diane and I traveled with a group of birders to New Mexico this January.  We started in Albuquerque and followed the river south.  Our group arrived at the Bosque del Apache National Wildlife Refuge in the pre-dawn glow.  As we stumbled from the van, we could hear a giant flock of geese honking on the pond before us.  As the eastern horizon lightened it revealed the gabbling geese. Before the sun was up, some signal went out and the geese took flight with a mighty roar of wings.  They circled over the water and our heads with a cacophony of calls.  Their numbers were so vast they blocked out the rising sun behind them.  The geese flew for a few minutes then returned to land on the pond.  They repeated this action several times, then after the sun was well up, they flew off to their daily feeding grounds.   

Snow Geese resting before dawn.

Snow Geese in flight.

Snow Geese are joined in the Rio Grande valley by thousands of Sandhill Cranes (Antigone canadensis) and tens of thousands of ducks.  There are also Canada Geese (Branta canadensis) mixed in and a smaller number of Ross’s Geese (Anser rossii) that look like miniature Snow Geese.

Video of Snow Geese flying at sunrise.

Snow Geese have two color forms or morphs, the white Snow Goose and the darker Blue Goose.  Both morphs have black primary feathers and a white head, but the Blue Goose has a dark gray body.  Snow Geese and Blue Geese have dark pink legs and bright pink beaks that bear a black “grin patch”.  The grin patch, or smile, is the serrated edge of both the upper and lower mandibles.  The geese use this feature to graze on the rough plant material that makes up much of their diet.  The color of Snow Geese is controlled a single gene and in New Mexico the white form predominates. 

White morph Snow Goose.

Dark morph Snow Goose (Blue Goose).

White and dark morph Snow Geese in flight. 

A Ross’s Goose is about three quarters the size of a Snow Goose with a shorter neck and a pink beak that lacks the black smile.   Ross’s Geese also come in the white and blue morphs but we did not see any of the darker form in New Mexico. 

 

A Ross's Goose (Anser rossii), left of center,
among Snow Geese. The Ross's Goose is smaller with a shorter beak 
shorter neck, and no grin patch. 

Our group made a second visit to Bosque del Apache, this time in the afternoon.  The white Snow Geese were shining on the pond and an adjacent dike.  Blue forms were mixed in and with careful observation we could pick out the smaller Ross’s Geese.  The geese were placidly feeding making their honking calls when suddenly the whole flock went silent.  Every goose, on land and water raised their heads and then geese at the edge of the pond took off.  The flight became a wave sweeping across the water toward us.  As closest geese passed over our heads we were pelted with goose poop.  Like many birds, the Snow Geese lighten their load for flight and we got spattered.  They say getting hit is good luck.  We were indeed a lucky group. 

 

White and dark forms of Snow Geese resting on a dike. 

Snow Geese in flight. 

While this spectacular flight of Snow Geese can inspire awe, there is a downside. Unlike many species of birds, Snow Geese numbers are increasing.  The last century has seen their population grow from a few hundred thousand in the early 1900s to over 5 million today.  This increase in population was driven by drainage of wetlands and the conversion of forest and prairie to agriculture.  The geese found waste grain left in the fields and their numbers boomed.  The large population of Snow Geese is an environmental problem on their breeding grounds in the high Arctic.  The geese are overgrazing the tundra and this is having a negative impact on other species that live and breed in the Arctic.  One attempt to lower the Snow Goose population is a longer hunting season and increased bag limits.  So far this has not solved the problem. The Snow Goose population problem was, of course, caused by a species that currently numbers 8 billion.

Snow Geese rising.

Despite the clouds on the ecological horizon caused by the large Snow Goose population, the wintering  geese are an amazing sight that ranks with the Monarch butterflies in Mexico and the Wildebeest migration in East Africa.   If you get a chance, go to New Mexico in winter and experience the flight of the Snow Geese.

Snow Geese overhead.