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Bird Trends (Hudson CBC 1986-2015)

//Bird Trends (Hudson CBC 1986-2015)

Bird Trends (Hudson CBC 1986-2015)

Prompted by the arrival in my inbox of the preliminary count data from the 2016 Hudson Christmas Bird Count and it being a bit chilly outside today – to say nothing of windy and with snow falling – I thought to myself, what better to be doing on New Year’s Eve than to crunch some numbers. I think people will find this interesting – at least, the sort of people I know 🙂

So – here are species bird counts from the Hudson CBC for the past 30 years, from 1986 up to 2015. I have omitted this year’s counts as they are still preliminary figures. Each chart below graphs the number of each species reported for each year and is overlaid with a curve showing the polynomial trend line for the period (exponential trend line for the Wild Turkeys as it’s a better fit). From these it is easy to see which way the populations of our winter birds have been moving in the past three decades. The species were more or less chosen at random from amongst those species with high enough counts most years to be reliable/significant. If anyone would like to look at the data themselves you can download counts for the past 76 years from the Audubon website and play to your heart’s content in the spreadsheet of your choice.

I would be interested in your comments on these data – please use the comment box at the bottom of this post. Thanks.

 

House Sparrow

I am perennially interested in House Sparrows, so this was the first out of the box. Not surprisingly, given what is happening elsewhere in the world, there has been a steady decline in numbers since around 1996 which in the past two or three years appears to finally be levelling off.

Blue Jay

Reasonably steady populations averaged over the thirty years with notable peaks and troughs on the actual census days. Worryingly low counts last year (and anecdotally in 2016 also).

Northern Cardinal

As expected – there is a clear upward trend in the numbers of Cardinals being seen in early winter.

European Starling

Numbers increased for the first ten years but then, with some year-to-year variation, have been reasonably consistent up to the presetn day.

Snow Bunting

Tend to be localised and move around in flocks so there is an element of chance in finding them in any year. Overall numbers were relatively consistent until the latter twn to fifteen years when there seems to have been a small but regular decline. Account must be taken, however, of great fluctuations from year to year.

Pileated Woodpecker

Low in number but showing a steady increases over time

Northern Shrike

A highly inconsistent bird only seen in small numbers but showing a trend towards lower numbers

American Crow

A gradual increase in the numbers counted over the years

Black-capped Chickadee

Generally present in consistent numbers year by year.

Mourning Dove

Interestingly, after an original increase in number they l;evelled off and in recent years are showing a definite decline in population.

Mallard

At first only very infrequently seen their numbers started to rise noticeable some twenty years ago. It is reasonable to ascribe this to climate change resulting in open water being still present at the time of the count day.

Wild Turkey

Not seen at all in the circle until 2005 these birds have moved in with a vengeance and show steadily increasing numbers year by year

Downy Woodpecker

Reliably consistent species

White-breasted Nuthatch

A slight but consistent increase in numbers

American Tree Sparrow

Consistent in small numbers with annual fluctuations but no definite trend up or down in populations over the thirty years.

Dark-eyed Junco

In many recent years barely seen at all but there is evidence of a steady or increased population. Insufficient data to be certain.

House Finch

After an initial increase in numbers in the first decade reviewed here, numbers have been generally consistent

 

By | 2016-12-31T17:58:36+00:00 December 31st, 2016|Uncategorized|2 Comments

2 Comments

  1. Connie 2017-01-01 at 11:15 - Reply

    Very interesting! Any thoughts on the reasons for the House Sparrow trend?

    • richard 2017-01-02 at 11:28 - Reply

      Probably the same as everywhere – multiple factors but change in habitat, reduction in available nesting sites, big changes in land use, agriculture etc etc. There has been much published on this in Europe in particular … worth googling. It’s very interesting.

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