The first time I ran into the conundrum of how to quantify the number of individuals in a large flock of birds was as at the edge of the Pacific Ocean at Boca Budi in southern Chile. On the cliff face overlooking the Pacific Ocean we encountered a colony of nesting Red-legged Cormorants (Phalacrocorax gaimardi). Our best estimated was that the visible portion of their cliff had a minimum of 300 individuals, a number that was likely an underestimate. Here is a link to the eBird checklist. The second time I ran into the same problem, albeit on a different magnitude, was at a small pond outside of Tofield (Alberta) full of snow geese (Anser caerulescens). Our best estimate was that there were 15000 geese on the water and in their air. Here is a link to the eBird checklist. Both times we had no particular estimation strategy, but rather we based our estimates on eyeballing and whatever “common sense” we had (whatever that means in this context). A few weeks ago we encountered a large flock of Canada Geese taking off from a farmer’s field outside of Camrose, this time I decided to go about the estimation more systematically by using one of the photos I took of the fleeing geese.
Once I had the photo on my computer screen I proceeded by according to the following steps:
I started by dividing up the image into a grid (see image below).
I counted each bird in the grid cell with a green outline. There were 23 individuals in this cell.
I used the patter from this cell to estimate the number of individuals in every other cell. The estimates are in yellow and fall into four categories, “looks like 23”, “looks like half of 23, i.e. 12”, “looks less than half, i.e. 5” or “no birds = 0”.
I added up the estimates (the yellow numbers) and got an estimate of 436 geese.
To check how good my estimated was I then counted the actual number of individuals in each grid cell (note the blue dots), indicated in blue numbers, and added it up. There are exactly 422 geese in the picture.
The estimate is not to shabby but obviously begs the question how one would (could) modify this approach to do “live” estimates in the field. I guess doing a “posts-observation” estimate like this is also fine to as long as all the birds are in the picture to start with.
The main issue with this estimate is that the image does not include all the geese. There were plenty more geese both to the right and left of the picture. This estimate was more a proof of concept exercise that still needs to be refined to be useful in the field when you have a gaggle of geese flying by in a matter of seconds.
I was at the Emerald Pond in Sherwood Park looking for charismatic birds such as pelicans. The pelicans were a no show, but there was plenty of Canada geese in the tall grass surrounding the pond. I did not pay much attention to the geese and as I was walking along the shore they kept a close eye on me and slowly, almost reluctantly, moved out of my way as I was approaching. As I approached one goose that appeared alone I noticed something else moving around in the grass right beside the goose. They were goslings and this would explain the slighly odd behaviour of the adult geese. The adult was herding the goslings towards the water’s edge while keeping its head high and its gaze fixed on me. As I started to scrutinize the other geese around the pond, now that I knew what to look for, I saw they all had little ones. The yellow goslings were remarkable well-camouflaged in the tall grass and obediently followed their moms and dads into the water. Once in the water the families quickly crossed the pond and got out of the water on the other side. I imagine the goslings might be safer in the tall grass as they would be easy prey for an opportunistic raptor in the open water.
Canada Geese are big birds with an even bigger attitude. There does not seem to be much that faze them. As probably one of the most common birds in these neck of the woods it easy to start ignoring them in favour of more exciting and uncommon birds. This fella, however, was out to make a statement that could not be ignored. Perched on the ridge of the roof of a large house overlooking the the Heritage Wetland Ponds, this Canada Goose was not lacking any self-confidence. I spend quit some time watching it and it seemed quite comfortable hanging out at its lofty and exposed perch. The only predators that could threaten an adult Canada Goose would be non-flying animals such as coyotes, cats (big cat, not your domestic kitty), foxes, dogs and humans. In other words, while this fella may be in an exposed location the biggest threat facing it would be inclement weather. Not on this day though, the sky was blue with not a cloud in sight and this goose was the king (or queen) of this roof.
The Canada Geese are back and with that, spring migration is slowly getting started. I spend the morning at Elk Island National Park and came across, what must be one of the most iconic Canadian sights, a bunch of Canada Geese making a racket on top of a beaver dam in a frozen lake. No sight of beavers though. I imagine, however, that the occupants of the dam must have been royally annoyed by being awoken so rudely by the geese. Not far away, I spotted a band of European Starlings chattering away in a tree. The starlings became species 42 on my Alberta Big Year list. It may be a slow start to spring but from now on it can only get better as the pace of the returning migrants quickens. There is much too look forward to as our familiar birding spots are about to get transformed. The bison were also out in full force, both the Plains and the Wood bison. I also saw some deer and a fleeting shadow at a forest edge in the distance eerily reminiscent of a moose, but maybe it was just an optical illusion combined with wishful thinking.
May the curiosity be with you. This is from “The Birds are Calling” blog (www.thebirdsarecalling). Copyright Mario Pineda.