Declining Bird Populations; Another False Global Warming Alarmism

Opinion; Dr. Tim Ball

Direct claims or inferences that global warming is causing decline or demise of bird populations are increasing. The Audubon Society has a along list, but there are also more references to individual species, such as the Kestrel, and the Swift. There are several regional claims, such as for America. They all assume or imply that anthropogenic global warming (AGW) is the culprit. Such claims are another example of exploitation of environmentalism and emotionalism for a political agenda. Like all the other alarmists claims, there is little or no scientific data or understanding of natural patterns and mechanisms, certainly, insufficient to make the claims being made.

Years ago, I peer reviewed an article submitted to a climate journal that claimed decline in population of a bird species on the Atlantic coast of South Africa, was due to human induced global warming (AGW). The article made no attempt to consider other causes. It was an early example of the pattern in the climate alarmist approach, that any decline or change in flora or fauna is due to human activity. The bird claims are a subset of the ill-informed extinction claims.

Movements of land based flora and fauna are different than for those atmosphere or ocean based. They react differently because they operate in fluid, three-dimensional space. This is true over all time spans. For example, it is noted about the Nautilus (Figure 1); In appearance, they have not changed much in millions of years.”

clip_image002

Figure 1: Nautilus

As their environment changes they adjust more quickly and with greater options. On a short-term basis, fisherpersons, (ugh), know fish vary their depth hourly with changing temperature gradients. Over time, the numbers and patterns of movement, change mostly with horizontal change in condition created by changing wind and ocean currents.

Lamb’s Volume 2 of Climate, Past, Present and Future had a section on changing patterns and distribution of birds, but did not look at other effects resulting from climate changes. It was part of my discussion with him about my thesis research. A subsequent article to a climate journal examined variations in date of arrival of geese on Hudson Bay with the spring migration. “The Migration of Geese, as an Indicator of Climate Change in the Southern Hudson Bay Region Between 1715 and 1851”, Climatic Change, Vol. 5, No. 1, 1983, pp. 83-93.

The major controlling factor was not the temperature but the wind patterns. The geese migrated most of the time (+80%) with a tail wind. On occasions, such as in the period from 1770 – 1790, geese arrived and overnight wind shifts from south to north, caused plummeting temperatures resulting in them being trapped in ice. The fur traders appreciated the opportunity for an easy goose hunt. Wind was also the most important factor in the South African case, as wind and ocean current reversals similar to the El Niño/La Nina occur. The important point about ocean current reversals are, they are caused by wind pattern reversals and that impacts the location and migration of bird species.

Bird populations fluctuate as much as animal populations, but the actual counts are much harder to establish because the birds move to different regions. Usually their movement is triggered and driven by changing wind patterns. In the late 1980s, there were reports of declining waterfowl populations across the Great Plains and its extension, the Prairies of Canada. Immediately the finger pointing began and mostly at agriculture. Clearing woodlands, draining wetlands and use of chemicals were all blamed. It was none of those; it was a drought almost equal in severity to the 1930s drought.

Where did the birds go? Wind patterns changed as the prolonged blocking system, that caused the drought to set in. The north/south flyway (Figure 3) shifted west and bird numbers in western and northwest Canada increased significantly. By the early 1990s, wind patterns shifted back, the rain returned and so did the waterfowl. Of course, there was no apology to the farm community.

Wind is the most neglected weather variable. It is very important for what it tells us about the weather creating mechanisms, but also because of its role in conversion and transfer of moisture and energy. Information about vertical winds, convection, and transport, especially in the Hadley Cell, are inadequate as evidenced by the IPCC AR5 comment that,

Most climate model simulations show a larger warming in the tropical troposphere than is found in observational data sets.

A major problem is that wind mechanisms in these regions are mostly massive convective cells of cumulonimbus that are too small to fit in the smallest grid of a computer climate model. Many birds use these convective winds to gain altitude and begin their migratory patterns.

In the middle latitudes most air moves horizontally. Technically, it is advection, but more commonly called wind. Birds migrate on these winds, so as they change the migration pattern changes. The greatest shifts are between Meridional and Zonal Rossby Waves (Figure 2).

clip_image004

Figure 2: Rossby Waves

North American wind patterns are also influenced by the Rocky Mountains. The result is a set of flyways followed by migrating birds on a seasonal basis (Figure 3).

Humans are directly killing birds and endangering a few unique species almost all by wind turbines. An alternate power source, a result of environmentalists ostensibly saving nature, is having opposite effects.

clip_image006

Figure 3: North American Flyways

Some suggest decline of certain bird species is due to wind farms. It is hard to determine the actual numbers of any one species killed by the turbines. Even a total estimate is unclear. Some endangered species are threatened, for example, Whooping Cranes

The only sustainable population of whooping cranes in the wild is declining, concurrently with the invasion of their migration route, the Central Flyway, by over 2,000 wind turbines and their power lines. Nearly one hundred of these critically-endangered birds were lost this year, i.e. one third of that population.”

T Boone Pickens, American oil billionaire, decided to exploit the wind turbine subsidies by building a massive wind farm. The problem is it was right on the major flyway and would have chewed up migrating birds. Within 3 years he abandoned the plan not to save the birds, but because of better opportunities, as subsidies disappeared and natural gas became cheaper.

Meanwhile the government didn’t abandon wind farms, but they did abandon the birds. There is a federal fine of $10,000, or a jail term of 1 to 5 years, for a person who kills an eagle. However, the US Fish and Wildlife Service (USFWS),

“has not prosecuted a single company for violating one of the many statutes protecting threatened endangered birds.”

Even worse, the Obama Administration has approved a quota of birth deaths per wind farm. As Michael Hutchins, of the American Bird Conservancy said,

“You can’t call it green if it’s killing hundreds of thousands of birds and bats annually and if it’s killing large numbers of protected eagles.

Reports of overall declining bird populations continue, as do claims of species decline. There are also a few reports of increasing populations, like one on woodpeckers. The reason was an increase in a food source, the Emerald Ash Borer (EAB). At least they didn’t attribute increase in EAB to global warming, but they did provide the source of their information.

“Participants in citizen science projects contribute real, valuable data that allow us to tackle some major ecological questions related to invasive species, urbanization and habitat change, our changing climate, or other factors,” according to David Bonter, Project Leader of Project Feederwatch and a co-author on the study. “FeederWatchers are a particularly dedicated group, contributing more than 4.2 million hours of observation since 1987 and allowing us to track changes in the abundance and distribution of birds across North America.”

Maybe these methods are too subjective, since they are by avid bird watchers, whose zeal is legendary and a focus of satire.

To underscore this problem, there are reports of increasing populations. For example,

“The BBC reports on a new study that suggests many European species of animals and birds have seen their numbers rebound dramatically. And that recovery has been going on for quite some time. In fact, many of the species studied had seen their numbers increase by as much as 3,000 percent since the 1960s.”

 

The trouble is these reports are as self-serving as the bird watcher’s reports. The increased numbers are attributed to government policy.

The researchers believe a combination of factors have been driving this return. Legal protection in the European Union, such as the birds directive and habitats directive, had helped to revive the fortunes of species, as had dedicated conservation schemes, said Mr. [Frans] Schepers [managing director of Rewilding Europe].

The same article provides another explanation.

It’s not all about legal protections and conservation policy, either. Much of the rebound may be due to increased urbanization and the abandonment of the countryside — leaving more room for animals to thrive.

So what is the truth? The answer is, bird populations fluctuate significantly in absolute numbers, just like all animal populations. They also fluctuate regionally as environmental conditions change. This is especially true of wind pattern changes on migrating birds.

Environmentalists, like the World Wildlife Fund (WWF) and alarmists, like Al Gore, always try to underscore their claims with threats to animals. They choose animals that people find attractive. These have appealing features like furry coats, preferably white, large round eyes, or manifest anthropomorphic behaviors. One way I underscore the point to people is to list many species increasing in numbers because of the new habitat opportunities. The list includes, snakes, rats, coyotes, mice, among others. Then stop and ask them, “Oh, have I mentioned any you like yet?”

People have a greater affection for birds than any other animals. They are symbols of freedom and beauty and as such a vulnerable vehicle for alarmist exploitations. As H.H. Munro said, “A little inaccuracy sometimes saves tons of explanation.” The trouble is, with all these cases, it is more than a little inaccuracy.

0 0 votes
Article Rating

Discover more from Watts Up With That?

Subscribe to get the latest posts sent to your email.

124 Comments
Inline Feedbacks
View all comments
John F. Hultquist
October 6, 2014 9:13 pm

Agree with this, natural patterns are important [that’s the topic], but some credit for the well being of wild life in North America ought to be given to human activities such as the Pittman–Robertson Federal Aid in Wildlife Restoration Act – hunting and fishing gear taxes. Other groups (there are many) such as Ducks Unlimited and other nature conservancy type organizations are helpful. Others will have to comment on such things in other countries.

Jimbo
October 6, 2014 9:30 pm

It’s amazing to think how a little global warming will wipe out birds. These creatures evolved from dinosaurs during the Jurassic Period.
http://www.nature.com/nature/journal/v461/n7264/abs/nature08322.html
http://www.livescience.com/47128-shrinking-dinosaurs-evolved-into-birds.html
Yet the WWF informs us alarmingly…

WWF
Birds suffer from climate change effects in every part of the globe. Scientists have found declines of up to 90 per cent in some bird populations, as well as total and unprecedented reproductive failure in others.
http://wwf.panda.org/about_our_earth/aboutcc/problems/impacts/species/cc_and_birds/

Send more donations please.

Jimbo
Reply to  Jimbo
October 6, 2014 9:32 pm

Here is the WWF supporting wind turbines and providing instructions on how you can make one.
http://wwf.panda.org/about_our_earth/teacher_resources/project_ideas/green_power/

tty
Reply to  Jimbo
October 7, 2014 2:05 am

Technically they aren’t lying. Notice that they don’t claim that the declines or reproductive failures have anything to do with climate change.

Jimbo
Reply to  tty
October 7, 2014 2:57 am

Technically they are trying to deceive by putting “climate change” just before the reported declines.

MarkW
Reply to  tty
October 7, 2014 5:40 am

Without better data, I still suspect that the claim of 90% declines are a complete lie.

nutso fasst
October 6, 2014 9:49 pm

I’ve seen the old birds-killed-by-cats numbers still being tossed out as an excuse for chopping and broiling of bird species that often prey on cats as well as on other birds.
The Smithsonian study often cited for the cat-kill claim was done by green-energy-supporting bird conservationists. Their inflated numbers come from a computer model that extrapolates numbers reported in other studies. The study–blabbed to the world by an unquestioning media–has been roundly criticized by other scientists as being sheer fabrication.
In my experience, well-fed domestic cats that roam free are more likely to come home with a rodent than a bird. Cats kill black rats that feed on bird eggs from nests not accessible to cats.
Many birds eat birds. Some seagull species feed on baby ducks, and even robins have been known to kill and eat the young of other birds that have fallen from nests.
In any case, the bird species commonly killed by cats are by no means endangered (quite the opposite, in fact). There is no relationship between cat predation and the chopping and broiling done in the name of enriching crony corporations.

October 6, 2014 10:22 pm

With wind turbines killing more than 573,000 birds each year in the United States, birds and bats would be well advised to crowd into Japan where they have the sense not to destroy their landscape with Avian-Chompers.

October 6, 2014 10:51 pm

I doubt the overall bird population is declining because we are producing 100 million tons of chickens every year. The equivalent weight of the entire human population every 3.5 years. If we start eating other bird species, their populations will increase dramatically.

Reply to  Dr. Strangelove
October 6, 2014 10:57 pm

BTW that’s annual poultry production, which includes chickens, turkeys, ducks, etc.

Alberta Slim
Reply to  Dr. Strangelove
October 7, 2014 6:57 am

Great.. Soon we may be getting Kentucky Fried Buzzard. ;^D

NOBODY
October 7, 2014 2:30 am
richard
October 7, 2014 2:34 am

Cats are now on 180,000 islands.
http://www.earthintransition.org/2012/08/are-cats-wiping-out-birds/
“New studies are giving strong evidence of just how many birds are being killed by cats – both pet and feral. In the United States alone, according to a new study, 500 million birds fall prey to cats every year, along with three billion other small animals”

Alberta Slim
Reply to  richard
October 7, 2014 6:59 am

Can this be an example of the so called “Balance of Nature”???

mpainter
Reply to  richard
October 7, 2014 7:59 pm

“Along with three billion other small animals”
They seem to be counting the fleas.

Editor
Reply to  mpainter
October 8, 2014 10:46 am

Reply to mpainter ==> There are interesting, fairly sound, studies on this point. Some of the best have been done using cat-mounted cameras to see what they spend their time doing.
In my personal experience, our cats kill baby rabbits (quite selectively), any nestling bird found, small birds, flying squirrels, baby squirrels, occasionally red squirrels (which are smaller than greys), voles and chipmunks — but ignore the mice in the pantry (with whom they share the nighttime hours) — and never full-grown rats.

mpainter
Reply to  mpainter
October 8, 2014 12:02 pm

Kip:
In my book rodents and rabbits are fair game for any predator-owls, foxes, coyotes, cats, whatever. I see no danger of running out of these and their fecundity assures their survival.
A camera mounted on a cat? Hard to visualize that.

October 7, 2014 2:46 am

“… can link an increase in CO2 levels with bird populaitons …” – difficult to do it (is it even possible?) particularly when, example, is such background (http://www.startribune.com/lifestyle/274551231.html):
“… other issues may pose even bigger — and much more immediate — problems for the state’s bird population. He’s [Henderson] particularly concerned about contaminants in lakes, especially lead used in fishing gear, that’s poisoning the loons. He also pointed to the loss of grasslands [I would add fragmentation of environments] and an increasing use of pesticides. “If people want to do something to help the loons, they can start requesting nontoxic, loon-safe fishing tackle,” he said.”
So not only “landscape changes” and “Millions of pet cats and night-light city buildings…” are significant.
In addition, negative factors may be offset by positive:
(Tryjanowski , 2014. http://www.plosone.org/article/info:doi/10.1371/journal.pone.0063482):
“Many recent studies have shown that arrival timing is related to temperatures en-route and at destination. Because urban areas are “heat islands”, with higher temperatures that influence earlier vegetation and invertebrate development, this should favour earlier arrival of migrant birds to cities rather than to rural areas.”
“To date, the timing of when birds return to their breeding area has been a key component of studies of the impact of climate change upon bird populations, because arrivals are strongly related to temperature.”
“A good example of warmer environments are cities, characterised by higher temperatures than their surroundings and hence sometimes called “heat islands”.”
“Because of higher temperature, urban environments may also supply an abundance of food due to higher primary productivity, a longer growing season …”
In the UK in 2013 were rejected 134 applications, only 141 were approved (wind farms). Are to be disposed of wind farms distorting radars (high number of accidents, a few airplane crashes) and new windmills can not be seen on radar. Windmill on the radar screen no different from a small plane.
Minister Michael Fallon: “… a large part of public opinion [especially England] is a negative attitude to wind farms.”
Therefore, the ratio of projects implemented to commenced, falls. With c. 70 percent to c. 35 percent.
Therefore, terrestrial wind farms “cut off” subsidies by 5 percent. Until March 2017 – 95 pounds for every megawatt hour of energy, from April 2017 – 90 pounds.

Alan the Brit
October 7, 2014 3:55 am

Deja vu!
The Royal Society for the Protection of Birds, (RSPB), which does very nicely out of huge grants of taxpayers funding from the EUSSR/PDRofEU, are constantly droning on about species reduction through Climate Change & habitat destruction, with a strong emphasis on the former. These are the ones who clamoured for Protected Species status for the Sparrow-hawk, the Magpie, etc. They then claimed CC was the cause of a C was the cause in the decline of Thrush numbers, Magpies eat Thrushes! The logic in incredible!

MarkW
October 7, 2014 5:25 am

Weren’t they blaming house cats a few years ago?

Editor
Reply to  MarkW
October 8, 2014 10:53 am

Yes — and it is still true, but only for small, low-nesting song birds and frequent bird feeder visitors, and only in urban areas where cats populations are so high.

October 7, 2014 7:09 am

Reblogged this on the WeatherAction News Blog.

Craig Loehle
October 7, 2014 7:37 am

National Geographic show the other day showing people catching migrating birds in North Africa in nets by the many millions. Desperate people will eat anything. Best cure is to help people raise their standard of living.

Alberta Slim
Reply to  Craig Loehle
October 7, 2014 8:35 am

But, they have to eat them raw, because they cannot burn fossil fuels to cook them………… ;^D

Frederik
October 7, 2014 8:19 am

i got a good question for those fear inducing “scientists” that seem to forget this: how did all those bird species manage to survive ice ages, sudden bond cycles and heinrich cycles where global temperature rises and fall several degrees in just a decade? How did they survive the – much warmer then today – Emian interglacial? if they did how can then a few tenths of degrees of warming suddenly “endanger” them?

LogosWrench
October 7, 2014 8:53 am

It would be nice if like doctors, scientists were held accountable for misdiagnosis. Maybe some of this alarmist hyperbole would go away.

Michael Oxenham
October 7, 2014 9:06 am

re Jimbo 9.10pm
Alan 3.55am
I cancelled my RSPB sub years ago. Could’nt stand their ecoloon ramblings any longer.

peter
October 7, 2014 11:23 am

I have read a few essays that claim that, despite efforts by the activists to claim otherwise, during the period when DDT was in wide use the Audubon census showed a large increase in bird populations, lack of parasites was listed as the reason.
Maybe the decrease is due to the fact that the long term effect of DDT in the water and soil is almost gone. the same reason we see Bedbug’s spreading like crazy.
Have no idea if this is in fact true.

BLACK PEARL
October 7, 2014 11:31 am

Dont know about birds buts the bats dont seem to know how to dodge those wind mills
http://www.ucdenver.edu/about/newsroom/newsreleases/Pages/Study-shows-wind-turbines-killed-600000-bats-last-year.aspx
Not much heard on this in the media … shocking & “worse than we thought”

October 7, 2014 12:35 pm

Audubon’s report is 90% nonsense but it doesn’t help when the Dr. Ball makes such a foolish statement as “Humans are directly killing birds and endangering a few unique species almost all by wind turbines.” Wind machines cause serious avian mortality but habitat loss, cats, tall buildings and power lines are even worse. The avian population loss from habitat loss due to the the insane “green” ethanol fuel program is much worse than the loss from wind. He is correct that many birds just move to better habitat, but there have been many serious losses (and gains) over the last several decades. Avian population estimates from such programs as the Breeding Bird Survey (I was part of the early development) are statistically reliable. The key trend they show is that grassland birds, the group mostly affected by growing more corn for ethanol, show by far the biggest decline. I’m working on a more serious and accurate rebuttal of Audubon’s insane climate report.
Richard Carlson, co-author, Solar Energy in America’s Future, Stanford Research Institute, 1977.

Editor
Reply to  rccarl
October 8, 2014 11:07 am

Almost all the bird declines are actually environmental habitat declines.
The State of the Birds organization (a combined effort of almost every conservation and wildlife group) [ see http://www.stateofthebirds.org ] places the blame for those birds that are declining on habitat loss:
Grassland birds: “Since 1968, the grasslands indicator for 24 obligate breeding birds declined by nearly 40%, but the decline flattened out beginning in 1990. This recent stabilization noted in the 2009 report continues today,…”
Aridland Birds: “Aridland Birds: “The aridlands indicator for 17 obligate birds—breeding birds of desert, sagebrush, and chaparral habitats in the West—is the most steeply declining of all habitat indicators, with an overall loss of 46% since 1968. Just since 2009 this indicator dropped 6%, extending a nearly continuous 44-year decline. Habitat loss and frag – mentation due to residential and energy development are the most consistent and widespread threats. Long-term habitat degradation from unsustainable land use, invasions of non-native grasses, and encroachment by trees and shrubs also play significant (and underappre – ciated) roles in the decline. These negative effects have been exacerbated over the past decade by severe drought, creating extremely difficult conditions for aridland birds such as Bendire’s and Le Conte’s thrashers,the two fastest declining species in the aridlands indicator.”
Coastal Birds: “The coasts indicator for 50 bird species that winter along U.S. coasts has steadily risen 28% above the baseline assessment in 1968, with an 8% rise over the past 5 years—a testament to the wise investments in more than 160 coastal national wildlife refuges and 595,000 acres of national seashore in 10 states.”
There are several more categories, but these suffice for examples here.
The significant thing is that NONE of these blame climate change or global warming. The SW US drought is consistent with the historical record of repeating lengthy droughts — and even that is not tied in their report to climate change.
It is ALL changing habitats — some of which are considered positive by other types of environmentalists — such as the abandonment of farms which revert to forest.

u.k.(us)
Reply to  Kip Hansen
October 10, 2014 9:20 pm

Yep, birds are good at filling niches, they’ve been doing it for millions of years.
Might be something to learn there ?

Bob
October 7, 2014 4:14 pm

How long can we support a population of whooping cranes that just refuses to multiply? When the bird disappears it will be a sad day, but this has been going on for decades and decades. Now, we have those damned windmills to worry about killing birds. How long can we play God with species that seem doomed, anyway?

October 7, 2014 6:31 pm

Cranes had multiplied 10 fold over the last 40 years or so until the #$%^&*( windmills started killing them.

David Ball
Reply to  rccarl
October 9, 2014 3:15 pm

But Dr. Ball’s statement is foolish.

Terry Stephens
October 8, 2014 12:41 am

When the Royal Society for the Protection of Birds, talk about climate change they mean of course increasing temperatures. What is missing from their assertion that this would be harmful to bird populations, is why? Holidaying in the Eastern Mediterranean, with summer temperatures regularly reaching 40C, you will commonly see breeding birds which you also find breeding in the UK; so not much similarity in climatic conditions there then.
My favourite two anomalies, and there are many, which point to the apparent unimportance of temperature in determining bird population and distribution are the Collared Dove(Streptopelia decaocto) and the Crested Tit(Parus cristatus).
The former, famously, until the 1940’s bred no closer to Western Europe than the area around the Bosphorous in the Eastern Mediterranean. By 1955, it was first recorded as breeding in England and now has colonised the whole of the UK and most of Europe. Evidently climatic conditions played no part in the massive expansion of this birds range.
The Crested Tit in the UK is confined as a resident breeding bird to a small part of Scotland. On continental Europe it is resident and breeds in a massive swathe from Scandinavia, through the Baltics and into Russia, all through Eastern and Western Europe, Germany, France(from the English Channel to the Mediterranean) and on into Spain and Portugal. The idea that the climate within it’s restricted range within Scotland, is more closely like the climate of Scandinavia and the Iberian Peninsula and hence favourable to the population, whereas the climate in the rest of Scotland and the UK is less favourable. is patently absurd.

PeterinMD
October 8, 2014 9:57 am

And then there was this last summer:
Rare bird last seen in Britain 22 years ago reappears – only to be killed by wind turbine in front of a horrified crowd of birdwatchers
The white-throated needletail is usually only seen in Asia and Australasia
Forty birdwatchers dashed to the Hebrides to catch a glimpse of this one
But as they watched it was knocked ‘stone dead’ after impact with turbine
Read more: http://www.dailymail.co.uk/news/article-2350267/Rare-bird-white-throated-needletail-killed-wind-turbine-crowd-twitchers.html#ixzz3FZcMXauG
Why don’t things like this bring more outrage from the general public? It boggles the mind.

October 8, 2014 11:25 am

From memory, the drought in the southern US a few years ago resulted in far fewer of a large bird being spotted (trumpeter swan/whooping crane size, in the traditional wintering area). Alarmists jumped on that.
But as usual with environmentalists they underestimated the birds – many had moved well to the northwest where feeding conditions were better.
Another case of population changes are snowy owls, who are partial to rodents such as lemmings. Every several years they show up in the lower mainland of B.C. where the wet fields and mudflats (such as Boundary Bay, one time they showed up in Renton at the SW end of Lake Washington) have voles. Many won’t survive the effort, it takes much energy for the journey and hunting. Other birds are more adaptable so stay north when lemming populations are low.
And Great Blue Herons, also not a particularly bright species, but they do follow food – the lower mainland and southern Vancouver Island in breeding season, nesting close to water, and hundreds of miles north between breeding seasons. Environmentalists want to claim they are a different species from those in SE BC but the populations have been mingling – for those in SE BC it saves the commute south to escape winter freezing.

October 8, 2014 11:36 am

Beware of bird counts.
The amateur ones in SW BC suffer from being a short session by volunteers. Worse, observations aren’t well distributed/organized for size and location. Big birds like Great Blue Herons are easier to spot than a few small birds, but there aren’t many so can be missed. And depending on food at that time some birds may be elsewhere enjoying their favourite food.
(Great Blue Herons are wading fishers but in winter in SW BC go to fields and eat rodents,
They are often spotted near ditches beside roads, including busy freeways. Some eco-nuts mistake their stillness for serenity, but it is essential to catching food – ripples in the water would alert prey.
And there may be an example of maximizing the combination of threats and food. For years Beacon Hill park in Victoria BC had a large heron colony despite its busyness. However they moved to Cuthbert Holmes park in nearby Saanich after one of a nesting eagle pair died. (Nesting eagles keep itinerant eagles away.)
The surviving eagle mated again, nesting in Beacon Hill Park again, so most herons moved back there. Presumably it is closer to some food source. While herons take turns foraging and guarding the nest, a longer foraging journey takes more of their energy. (When not nesting they can roam more, as they just sleep locally wherever the are finding food.).

johanna
October 8, 2014 10:09 pm

Bird counts are mostly mumbo-jumbo, for reasons well articulated by people above.
As someone pointed out, human activity can be very beneficial to birds. Broadacre crops are an absolute bonanza for birds that formerly had to scrounge for food. Where I live, an artificially created city, complete with lakes and millions of introduced European trees (chock full of fruit and nuts) has massively increased the native bird population.
Measuring bird populations and drawing conclusions is on a par with measuring “the temperature of the planet” in terms of scientific rigour, IMO.