First, the bees began to disappear and die off. Now, the birds are following suit. How will future generations explain the facts of life to their children?
From the New York Times:
Meadow Birds in Precipitous Decline, Audubon Says
Spreading suburbs and large-scale farming are contributing to a precipitous decline in once common meadow birds like the Northern bobwhite, the Eastern meadowlark, the loggerhead shrike and the field sparrow, a report released yesterday by the Audubon Society said.
Twenty common birds have lost more than half their populations in 40 years. The population of the bobwhite, a rotund robin-size bird that lives in meadows from the mid-Atlantic to the Plains, has dropped more than 80 percent, to 5.5 million from more than 31 million.
The evening grosbeak, with a range from northern New England to the Pacific Northwest, has declined 78 percent, to 3.8 million from 17 million.
The report covers a period when suburbs and exurbs were being carved out of Eastern and Midwestern farmlands and Southern wetlands. It also documents the loss of large numbers of Canadian and Arctic birds like the mallard-like greater scaup, the Northern pintail and the greater tern, all affected by a combination of climate change and development along lakes and rivers. [full text]
Kmareka.com 
The swings in numbers of individuals in any animal (or plant) species would seem to be a simple measurement (just count them!) and then figure out the reason(s) for that change. Unfortunately, even in the best of all possible worlds, the degree of accuracy attainable is less than adequate except in populations that have very narrow ranges–they may only exist in one place or environment for example. Over the 4.6, billion year history of this world living organisms have existed perhaps 3.7 billion years. Something MORE than 99% of all the life forms that have ever existed on this planet for those 3,700,000,000 years are extinct. That remaining 1% that basically includes all living organisms concists of perhaps 1.2 million different kinds of organisms; all the bacteria, fungi, algae, trees, insects, etc., etc. Most of the living forms are obviously bacteria and insects, for example, and vertebrates (fishes, reptiles, birds, mammals) as I recall number about 75,000 or so species (I am away so have not checked these numbers, but I am in the right ballpark). There are about as many fish species as birds and fewer species of mammals.
Organisms go extinct for many reasons and as I suggest above, almost all organisms (99%) that have ever lived are extinct. The 1.2 million number of living forms is only about what we now have identified. That number is inadequate and may actually represent 5% or 20% of the actual number–there is not much funding or employment for scientists who go out and find and “name” new organisms. If there are actually 5 million living forms or 10 million, that number will still be only 1% of all the organisms that ever lived.
Each organism that ever lived tells its own story of origin, living and extinction, and that story will be very complex although there are some basic causes for species or groups of species to go extinct. There is one very significant new factor in the extinction story that maes the last 3-5,000 years different from the previous 3.7 billion or so. That is the landscape and environmental modifying abilities of one species, Homo sapiens in a neolithic, metal using, herding and agriculture, city building and landscape modifying cultural millieu. Species have become extinct in the past (and new ones evolved) in a Darwinian dominated world impacted by vast swings in land and continents, pulses of the Sun, changes in climate, impacts from outer space, and a myriad of “natural” events. Life on earth today is what I have termed, human dependent. Humans can and do determine what species will survive or go extinct. We do that either by neglect (not paying attention); determined efforts (killing all those bad germs, or competing plants, or elephant herds that eat our crops), or by “progress” (one more housing development in Florida, or draining a swamp in Asia, or by uncontrolled pollution from new factories or dams in China. Habitat impairment or reduction by “progress” is clearly an impact of increasing population of one species (us) to the detriment of all other life forms. If our population can be controlled, and enlightened awareness of the other inhabitants of this planet realized, solutions become possible. We will not stop continental drift and Indian will continue to bash into Asia raising those mountains, but we will allow organisms to find the habitat they need. The United States has breached the 300 million humans line within its borders. With a doubling time of 45 years, we will be at 600 million by 2057, and perhaps over 1 billion by the next century. The new suburbs and roads and all the other needs of 1 billion Americans will only be made by sacrificing what remains of the untouched landscape.