Early on, Thomas and Lennon (1999) analyzed the distributions of British birds over a 20-year period of global warming, looking for climate-induced changes in their breeding ranges. In doing so, they found that the northern margins of southerly species' breeding ranges shifted northward by an average of 19 km from 1970 to 1990; while the southern margins of northerly species' breeding ranges shifted, in the mean, not at all, which finding was stated by them to be similar to results obtained for European butterflies, "for which the northern margins have expanded more than the southern margins have retracted." Consequently, both British birds and European butterflies have expanded their ranges in the face of global warming, which is clearly a positive response that makes extinction much less of a possibility than it was before the warming.

Simultaneously, in America, Brown et al. (1999) had been studying a natural population of individually recognizable, color-banded Mexican jays in the Chiricahua Mountains of Arizona over the period 1971-1998 for trends in egg-laying dates and monthly minimum air temperatures. Over the 29-year period of their study, they determined that the date of first nest construction occurred 10.8 days earlier, while the date of first clutch in the population came 10.1 days earlier. These changes were associated with significant upward trends in monthly minimum temperature in the study area, of which they said that in many bird species "breeding is timed so as to have young in the nest when the principal food of the nestlings is at its peak." And with warmer minimum temperatures occurring earlier and earlier over their study period, they suggested that this climatic trend could be producing an earlier abundance of such food, which would help to explain the increasingly-earlier egg-laying date.

The three researchers also identified a second way in which earlier-occurring warmer night temperatures may lead to earlier breeding dates in birds: by alleviating thermal stresses on females on cold nights. Citing several studies that had revealed similar breeding trends in European birds, they suggested that the "recognition of similar trends on both continents in very different environments is consistent with the interpretation that some avian populations are already responding to climate changes in the last 29 years or so." And once again, these widespread changes are positive in nature, for not only are bird ranges increasing in size as air temperatures rise, the temporal availability of food needed to sustain important life processes is advancing in synchrony with the timing of egg laying.

Five years later back in Europe, Brommer (2004) categorized birds of Finland as either northerly (34 species) or southerly (116 species) and quantified changes in their range margins and distributions from two atlases of breeding birds, one covering the period 1974-79 and one covering the period 1986-89, in an attempt to determine how the two groups of species responded to what he called "the period of the earth's most rapid climate warming in the last 10,000 years," citing McCarthy et al. (2001). This exercise revealed that southern species experienced a mean poleward advancement of their northern range boundaries of 18.8 km over the 12-year period. However, the southern range boundaries of the northern species remained essentially unaltered. Noting that similar results had been obtained for birds in the United Kingdom (Thomas and Lennon, 1999) and other species (primarily butterflies) elsewhere (Parmesan, 1996; Parmesan et al., 1999), Brommer thus concluded that "in general, for northern hemisphere species, southerly range margins of species are less responsive to climate change than the northerly margins," demonstrating once again that the ranges of birds (and possibly other animals) in a warming world will likely increase in size, as their northern range boundaries expand poleward and upward while their southern range boundaries remain largely unaltered, which should render them less subject to extinction than they are currently or than they have been in the past.

Also working in Europe using data from the Breeding Bird Atlas of Lake Constance, which borders Germany, Switzerland and Austria, Lemoine et al. (2007) analyzed the impact of land-use and climate changes on the region's abundance of Central European birds between the periods 1980-1981 and 1990-1992, and between 1990-1992 and 2000-2002. This work revealed, in their words, that "the total number of [bird] species in the Lake Constance region increased from 141 species in 1980 to 146 species in 1990 and to 154 species in 2000," while "winter temperatures increased by 2.71°C and spring temperatures increased by 2.12°C over the 23 years from the first to the last census." These and other data thus led them to conclude that "increases in temperature appear to have allowed increases in abundance of species whose range centers were located in southern Europe and that may have been limited by low winter or spring temperature." In addition, they report that "the impact of climate change on bird populations increased in importance between 1990 and 2000 and is now more significant than any other tested factor [our italics]," which is a very important finding because the warming has tremendously benefited European birds and helped to buffer them against extinction.

Contemporaneously, for the portion of the United States located east of the Rocky Mountains, Hitch and Leberg (2007) used data from the North American Breeding Bird Survey to evaluate shifts in the northern range boundaries of 26 species of birds with southern distributions and the southern range boundaries of 29 species of birds with northern distributions between the periods 1967-1971 and 1998-2002. As a result, they found that the northern margins of the southern group of birds showed significant northward shifts that averaged 2.35 km per year for all species studied, which finding they describe as being "consistent with the results of Thomas and Lennon (1999) from Great Britain." Also in agreement with the behavior of British birds, they determined that "levels of warming do not appear to be so great they are forcing birds to abandon the southernmost portions of their distributions," which finding is also popping up in various places around the world.

Taking a look at the entire globe, Jetz et al. (2007), as they describe it, "integrated the exposure of species to climate and land-use change through the combined effects of these drivers on global land cover and explored the resulting reductions in range size and possible extinctions within the world's 8,750 terrestrial bird species," using the simplifying assumption of stationary geographic ranges that allowed them "to quantify risk in terms of the projected vegetation changes across a species' current range." This assumption, as they readily admit, "yields worst-case projections," but it provides a "first baseline assessment" of the relative strengths of the impacts of projected global warming and anthropogenic land-use changes on bird habitats worldwide.

Although the three scientists' simplistic analysis suggests that "expected climate change effects at high latitudes are significant" -- where, of course, researchers have observed nothing but positive responses -- it indicates that species most at risk are predominantly narrow-ranged and endemic to the tropics, where large range contractions are driven by anthropogenic land conversions. As a result, they thus conclude that this "habitat loss in economically emerging tropical countries will continue to pose an even more direct and immediate threat to a greater number of bird species," such that "even the most optimistic scenarios lead to substantial range contractions of species, especially of those already vulnerable to extinction because of their current restricted ranges."

Clearly, therefore, great harm to earth's many bird species will likely be caused by man's destruction of natural ecosystems -- in order to use the land and water resources that have historically sustained those ecosystems for the growing of food crops (needed to sustain our growing numbers) and biofuels (wrongly believed to be effective in fighting rising temperatures) -- and this anthropogenic phenomenon will be most strongly expressed in "economically emerging tropical countries" that can least afford to bear the brunt of its catastrophic negative consequences.

One year closer to the present, Halupka et al. (2008) documented various breeding parameters of reed warblers (long-lived passerine birds that spend their winters in Africa but breed in the reed beds of marshlands in the Palaearctic, with some of them nesting in fishponds of southwest Poland) during twelve breeding seasons (1970-73, 1980-83, 1994, 2003 and 2005-06) that encompassed the period 1970-2006, after which they compared trends in what they measured with concomitant trends in mean monthly temperatures. This work revealed that mean breeding season (April-August) temperature increased significantly between 1970 and 2006, as did the mean temperature of each individual month of the breeding season, with the average temperature for the May-July period rising by 2°C. And in response to these changes, they found that in 2005 and 2006, egg-laying (as assessed by the first-egg date of the earliest pair of breeding birds) started three weeks earlier than in 1970, and that the median first-egg date shifted forward in time by eighteen days. The end of egg-laying, however, did not change significantly in either direction, so there was a corresponding increase in the length of the egg-laying period.

With this longer laying period available to them, more birds were able to rear second broods. In the 1970s and 1980s, for example, the Polish researchers report that "only about 0-15% of individuals laid second clutches," but that "between 1994 and 2006 up to 35% of birds reared second broods." In addition, they report that "during seasons with warm springs, early nests were better protected by being hidden in newly emerged reeds," and that, "as a result, these nests suffered fewer losses from predation." Hence, they concluded that "the studied population of reed warblers benefits [our italics] from climate warming," as is clearly becoming the norm with most every species of bird that is studied.

A case in point is described by Jensen et al. (2008), who state that "global climate change is expected to shift species ranges polewards, with a risk of range contractions and population declines of especially high-Arctic species," citing contentions of the Arctic Climate Impact Assessment (ACIA, 2005). To better evaluate this claim, the six researchers constructed species distribution models for the Svalbard-nesting pink-footed goose (Anser brachyrhynchus), in order to "relate their occurrence to environmental and climatic variables," after which they used the most parsimonious of these models to "predict their distribution under a warmer climate scenario," based upon "mean May temperature, the number of frost-free months and the proportion of moist and wet moss-dominated vegetation in the area," the latter of which factors is "an indicator of suitable feeding conditions."

The results of this exercise indicated, in the words of the six scientists, that global warming "will have a positive effect on the suitability of Svalbard for nesting geese in terms of range expansion into the northern and eastern parts of Svalbard which are currently unsuitable." And they note that this result does not even consider the likelihood that glaciers will decrease in size and expose still more potential nest sites. Hence, they conclude their paper by stating that increased temperatures could release the population of pink-footed geese from the "present density-dependent regulation during the nesting period," and that "elongation of the frost-free season in Svalbard may relax their dependence on the acquisition of body stores before arrival (so-called 'capital' breeding, sensu Drent and Daan, 1980), so that geese will have more time to acquire the necessary resources upon arrival and still breed successfully," noting that "both factors are likely to have a positive effect on the population growth."

In another relevant study, based on bird-ringing records covering a time span of 41 years (1964-2004), Husek and Adamik (2008) "documented shifts in the timing of breeding and brood size in a long-distance migrant, the Red-Backed Shrike (Lanius collurio) from a central European population," after which they compared their results with the climatic history of the region over the same time period. In doing so, they determined that temperatures in May significantly increased over the period of their study; and they say that "in line with this increasing May temperature" there was "a 3- to 4-day shift towards earlier breeding," which pattern, in their words, "is consistent with the results of similar studies on other long-distance migrating songbirds (e.g., Dunn, 2004)." In addition, they report there was "an increase in brood size by approximately 0.3 nestlings since 1964." And of this latter finding they say that "given that early broods are usually larger (Lack, 1968; this study) and that they have a higher nest success (Muller et al., 2005), this may have a positive effect on future population increases as the temperature continues to rise."

About the same time, Seoane and Carrascal (2008) wrote that "it has been hypothesized that species preferring low environmental temperatures, which inhabit cooler habitats or areas, would be negatively affected by global warming as a consequence of the widely accepted increase of temperature during the last two decades," while additionally noting that "this effect is assumed to be more intense at higher latitudes and altitudes because these areas seem to be changing more rapidly." Hence, they devised a study "to assess whether population changes agree with what could be expected under global warming (a decrease in species typical of cooler environments)," focusing on birds.

Working in the Spanish portion of the Iberian Peninsula in the southwestern part of the Mediterranean Basin, the two researchers determined breeding population changes for 57 species of common passerine birds between 1996 and 2004 in areas without any apparent land-use changes. This work revealed, in their words, that "one-half of the study species showed significant increasing [our italics] recent trends despite the public concern that bird populations are generally decreasing," while "only one-tenth showed a significant decrease."

In discussing their findings, Seoane and Carrascal state that "the coherent pattern in population trends we found disagrees [our italics] with the proposed detrimental effect of global warming on bird populations of western Europe." And they are not the only ones to have come to this conclusion. They note, for example, that "one-half of terrestrial passerine birds in the United Kingdom exhibited increasing recent trends in a very similar time period (1994-2004)," citing Raven et al. (2005); and they note that "there is also a marked consistency between the observed increasing trends for forest and open woodland species in the Iberian Peninsula and at more northern European latitudes in the same recent years," citing Gregory et al. (2005). Likewise, they write that "Julliard et al. (2004a), working with 77 common bird species in France, found that species with large ecological breadth showed a tendency to increase their numbers throughout the analyzed period."

In further commenting on their findings, Seoane and Carrascal say that in their study, "bird species that inhabit dense wooded habitats show striking patterns of population increase throughout time." Noting that "this is also the case with those bird species mainly distributed across central and northern Europe that reach their southern boundary limits in the north of the Iberian Peninsula," they speculate that "these short- to medium-term population increases may be due to concomitant increases in productivity," citing the thinking of Julliard et al. (2004b) and the empirical observations of Myneni et al. (1997), Tucker et al. (2001), Zhou et al. (2001), Fang et al. (2003) and Slayback et al. (2003), whose work figures prominently in establishing the reality of the late 20th-century warming- and CO2-induced greening of the earth phenomenon, which has produced, in the words of the Spanish scientists, "an increase in plant growth or terrestrial net primary production in middle latitudes of the Northern Hemisphere since the 1980s, particularly in forest environments."

It should be quite clear from these several observations, therefore, that the supposedly unprecedented warmth of the last two decades has not led to what Seoane and Carrascal call "the proposed detrimental effect of global warming on bird populations of western Europe." In fact, it appears to have done just the opposite, with a little help, we might add, from one of man's and nature's very best friends: the historical rise in the air's CO2 content.

Back in America, after observing two second clutches in a newly established population of tree swallows in the Shenandoah Valley of Virgina (USA), Monroe et al. (2008) monitored all late nests in the following two breeding seasons to see what they could learn about the phenomenon. This surveillance revealed that "among all females nesting in the early breeding rounds of 2006 and 2007, 5% of birds with successful first clutches later laid second clutches." In addition, they report that the mean productivity for double-brooded females for 2006-2007 was 4.4 ± 1.3 fledglings from first clutches and 3.4 ± 0.8 from second clutches, so that "double-brooded females significantly increased their total annual productivity compared to birds nesting only in the early rounds of breeding." In fact, the productivity of the double-brooded females was approximately 75% greater than that of the single-brooded females. And in summing up the discussion of their findings in the concluding paragraph of their paper, Monroe et al. say that, "in general, late summer and fall nesting among North American birds is underappreciated and may be increasing due to global warming," citing the work of Koenig and Stahl (2007). If this is indeed the case, it would appear that the ongoing CO2-induced greening of the earth is beginning to work its way up the trophic ladder to the animal kingdom as well.

Noting that "climate envelopes (or the climatic niche concept) are the current methods of choice for prediction of species distributions under climate change," Beale et al. (2008) remind us that "climate envelope methods and assumptions have been criticized as ecologically and statistically naive (Pearson and Dawson, 2003; Hampe, 2004)," and that "there are many reasons why species distributions may not match climate, including biotic interactions (Davis et al., 1998), adaptive evolution (Thomas et al., 2001), dispersal limitation (Svenning and Skov, 2007), and historical chance (Cotgreave and Harvey, 1994)." Thus, in an attempt to shed more light on the subject, they evaluated the degree of matchup of species distributions to environment by generating synthetic distributions that retained the spatial structure of observed distributions but were randomly placed with respect to climate. More specifically, "using data on the European distribution of 100 bird species, [they] generated 99 synthetic distribution patterns for each species," and "for each of the 100 species, [they] fitted climate envelope models to both the true distribution and the 99 simulated distributions by using standard climate variables," after which they determined the goodness-of-fit of the many distribution patterns, because, as they describe it, "there has been no attempt to quantify how often high goodness-of-fit scores, and hence ostensibly good matches between distribution and climate, can occur by chance alone."

In a rather surprising result, the three UK researchers determined that "species-climate associations found by climate envelope methods are no better than chance for 68 of 100 European bird species." And, in their words, "because birds are perceived to be equally strongly associated with climate as other species groups and trophic levels (Huntley et al., 2004)," they say their results "cast doubt on the predictions of climate envelope models for all taxa." Hence, they conclude that "many, if not most, published climate envelopes may be no better than expected from chance associations alone, questioning the implications of many published studies." The bottom line with respect to our stewardship of the earth is thus well described by their conclusion that "scientific studies and climate change adaptation policies based on the indiscriminate use of climate envelope methods irrespective of species sensitivity to climate may be misleading and in need of revision," as is also evident from the results of the many studies we have reviewed in this brief analysis of the subject.

Continuing our enlightening journey through the ever-increasing number of studies devoted to determining global warming effects on birds, we come to the work of Grandgeorge et al. (2008), who analyzed population sizes and phylogenetic and spatial structures of British and Irish seabirds based on "(1) presence or absence of the seabird species in the different counties of Britain and Ireland between 1875 to 1900 and 1968 to 1972, (2) seabird breeding censuses of Britain and Ireland from 1969 to 1970, 1985 to 1988 and 1998 to 2002, (3) at-sea abundance and distribution surveys of seabirds in the North Sea from 1980 to 1985 and 1990 to 1995, and (4) a bioenergetics model to estimate energy expenditures for 40 seabird species." This work revealed, in their words, "a marked expansion in the breeding range of seabirds in Britain and Ireland between 1875 and 1972." In addition, they report that total seabird numbers "increased at an average rate of 1% per annum between 1969 and 2002, with a related increase of 115% in predicted total seabird predation." What is more, they state that "between 1875 and 1972 no seabird species was lost and there was an overall expansion in breeding range of the seabird population of Britain and Ireland, with the number of counties occupied increasing from 31 to 47."

As a result of these several findings, the six scientists concluded that "the seabird community of Britain and Ireland has been remarkably resilient to environmental change in the 20th century." In fact, they say it actually "prospered during the 20th century," and that "significantly raised ocean temperatures in the North Sea (Beaugrand, 2004)" may even have "created more favorable environmental conditions for some seabird species," citing the work of Thompson (2006), which conclusions are a whole lot different from the "end of the world" scenarios painted by so many climate alarmists.

In much the same vein, Brommer (2008) writes that a "population-level change expected under a climate-warming scenario is a poleward shift in the distribution of organisms," and he says it is thus believed by many that birds that "do not shift their range margin consist of species that are declining, and would therefore be of particular management concern."

A few years earlier, Brommer (2004) had measured the range sizes and northern range margin locations of 116 bird species with a predominantly southern distribution in Finland; and of those species he notes that "the trend slope describing the change in their abundance for the period 1983-2005 was calculated for 53 species by Vaisanen (2006)," which resulted in "the largest dataset available of the long-term trends in population numbers of Finnish birds that is comparable across species, because it has both been gathered and analyzed using the same procedures." Therefore, to complete the behavioral picture of the latter 53 species, Brommer (2008) determined the concomitant changes in their northern range margins.

The Finnish bird specialist found, in this regard, that "species foraging in wet habitats had experienced strong range margin shifts as compared with other feeding ecologies." But he said he found "no evidence that those feeding ecological groups that showed a relatively small shift in range margin had experienced low population growth or a population decline." Consequently, in discussing "the lack of correlation between the shift in range margin of the different feeding ecologies and the change in their mean abundance," Brommer states that this real-world finding "is contrary to expected under a climate-change scenario, because, all else being equal, a clear range-margin shift should indicate a good capacity to track climatic change, which should result in a more positive trend in abundance if climate change is indeed the main driver of population-level change." Once again, therefore, another of the doom-and-gloom prognostications of the world's climate alarmists -- i.e., that species that cannot, or will not, move in synchrony with shifting climatic zones must decline in numbers and possibly go extinct -- has encountered another set of real-world data that fails to substantiate it.

In another revealing study, Maclean et al. (2008) analyzed counts of seven wading bird species -- the Eurasian oystercatcher, grey plover, red knot, dunlin, bar-tailed godwit, Eurasian curlew and common redshank -- made at approximately 3500 different sites in Belgium, Denmark, France, Germany, Ireland, the Netherlands and the United Kingdom on at least an annual basis since the late 1970s. This they did in order to determine what range adjustments the waders may have made in response to concomitant regional warming, calculating the weighted geographical centroids of the bird populations for all sites with complete coverage for every year between 1981 and 2000.

This work revealed, in the words of the seven scientists, that "the weighted geographical centroid of the overwintering population of the majority of species has shifted in a northeasterly direction, perpendicular to winter isotherms," with overall 20-year shifts ranging from 30 to 119 km. In addition, they report that "when the dataset for each species was split into 10 parts, according to the mean temperature of the sites, responses are much stronger at the colder extremities of species ranges." In fact, they found that "at warmer sites, there was no palpable relationship [our italics] between changes in bird numbers and changes in temperature." Hence, they concluded that "range expansions rather than shifts [our italics] are occurring" as the planet warms.

In discussing the significance of their findings, the members of the international research team say that the commonly used climate-envelope approach to predicting warming-induced species migrations -- which is the one employed by Al Gore and James Hansen -- "essentially assumes that as climate alters, changes at one margin of a species' range are mirrored by those at the other, such that approximately the same 'climate space' is occupied regardless of actual climate," but that their work suggests "that this may not be the case: climate space can also change."

In further discussing their important finding, Maclean et al. write that "it is actually not surprising that responses to temperature appear only to be occurring at the colder extremities of species ranges," for they note that "it has long been known that it is common for species to be limited by environmental factors at one extremity, but by biological interactions at the other," citing the work of Connell (1983) and Begon et al. (2005). Hence, they conclude that it is likely that "the warmer extremities of the species ranges examined in this study are controlled primarily by biotic interactions, whereas the colder margins are dependent on temperature."

Last of all, we come to the study of Dyrcz and Halupka (2009), who examined long-term responses in the breeding performance of Great Reed Warblers (living on fish ponds near Milicz in southwest Poland) during various years from 1970 to 2007 (1970-1974, 1981-1984, 1997, and 2004-2007), over which period mean temperatures during the egg-laying months of the species (May-July) rose by a remarkable 2.2°C, from 15.3 to 17.5°C. In the course of this study, the two researchers found a "significant advancement in both earliest and annual [our italics] median first-egg-laying dates" that "correlated with temperature increases early in the season." Latest first-egg-laying dates, on the other hand, remained unchanged, as did several other breeding statistics, including clutch size, nest losses and number of young per nest. Consequently -- and contrary to a Bavarian population of Great Reed Warblers that also advanced its latest first-egg-laying date -- the Polish bird population expanded its breeding season in response to regional warming, whereas the Bavarian birds merely shifted theirs, as documented by Schaefer et al. (2006).

The two researchers thus concluded that "the studied population does not benefit from climate warming (as found in Bavaria), but apparently does not suffer," reiterating that "the Great Reed Warbler has adapted well ... by shifting the timing of breeding." Hence, they say the results of their study "do not confirm the prediction of Bairlein and Winkel (2000) that long-distance migrants would suffer due to climate change." In addition, they state that a comparison of their data with that from the Bavarian population "provides evidence that different populations of the same species can adapt in different ways to climate change," noting that "this was also previously found for woodland species," citing the work of Visser et al. (2002) and Sanz (2003).

In concluding this review, it should be obvious to most fair-minded individuals that earth's birds have not only not been harmed by the supposedly unprecedented global warming of the past few decades, they in many cases have actually been helped.

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