Yes, that happens here in Texas periodically, when we have extreme heat early in the year. When it happens, my husband always goes out and does a nest check (looking for attendant adults or bodies under the nests) on all the raptor nests he monitors locally, and there's always a sample of young nestlings that presumably either 'cooked' in the nest and were expelled or those that presumably flailed around too much and fell out (or if slightly older attempted to fledge too early). But presumably lots more nestlings die in those events than we actually see, b/c we usually get a round of nest 'failures' where the adults are suddenly no longer in attendance, which means the nestlings died in the nest from heat or the adults had to leave the nest too often to bathe or drink, and the nestlings were too exposed to the sun or were predated by jays or squirrels or opossums or some such.
Of course, we also get this kind of thing after intense storms (nestlings killed by hail or blown out of nests), but it's not as noticeable.
Here's some typical pics from a couple such recent episodes.
It's depressing.
That's kind of surprising. You'd think the birds in TX would have adapted given that extreme heat is semi-normal there.
That might be a bit of a misunderstanding of what adaptation means, in a practical applied sense.
First, animals that are evolutionarily adapted to the average conditions of their habitat will nevertheless often die or experience reproductive failure during years, months, weeks, or even days where the conditions fluctuate widely through the range around that average, particularly if the timing is 'bad' (e.g., coincidental nestling/downy age, which typically only lasts a month or so). For example, if a heat wave happens in early July, it's likely to kill a lot more of this particular raptor species' nestlings than if said heatwave occurs in May (while the birds are nest building) or later in the summer (when the nestlings are feathered out and more mobile). Likewise, violent thunderstorms involving high winds and sometimes huge hail are normal here during the summer, but they kill native (and thus well-adapted) birds every single year, by blowing nests out of trees or by violent impact with hail. Animals often don't adapt (in an evolutionary sense) to THAT fine of a scale of stochasticity (isolated incidents of e.g., fires, extreme drought, violent weather, food source failure, disease outbreaks). Now it is true that, with enough selective pressure on a population over very long periods of time, some species might evolve toleration to e.g., a degree or two more at the upper range of temperatures, if that becomes the norm for this region, but such evolutionary adaptation depends on multiple factors and is not a given.
Second, many people confuse the layperson's use of the word 'adapt', which means flexibility of behavior/learning that individual animals exhibit/might be capable of, with scientists' use of 'adapt', which means a change in a population's genetic and phenotypic characteristics over time (that is, 'evolution'). Behavioral flexibility can sometimes be one of the factors that influences evolution, but individuals themselves do not adapt or evolve under the scientific definition. So for example, some individual raptors (of the species I noted above) might build nests at sites with slightly worse thermal cover (more open canopies) and thus lose their young in a heat spike, while other individuals build nests in more shaded locations. If a clutch is lost with sufficient time to re-nest, usually the parent birds will build a nest at a new site (indicating at least some level of 'learning' that their old site wasn't suitable for whatever reason) and might be more successful the second time. That isn't evolution or adaptation, though...all the birds in the population are more or less equally 'adapted' to the area. That's just individual variation in behavior, randomness of nest site options available, and luck.
The problem develops when the habitat conditions change, especially if they change rapidly, beyond what animals can adjust to either behaviorally or physiologically, esp if the change occurs at a scale and frequency that impairs reproductive success to the point that the population becomes nonviable in the long term. The species might not be completely extirpated from the area b/c the basic elements of suitable habitat might still be there (food, cover, nest sites, etc), but the population might no longer be able to self-sustain.
The converse situation can happen too...For example, over the past 20 years as climate change has caused average temps to creep up in the southwest, the formerly desert-limited Harris' hawks have begun showing up far north of their previous range (the range to which they are unquestionably evolutionarily adapted). They are limited by cold more than heat in the U.S., and as climate change has changed conditions, they've begun occasionally reproducing around our city in northern TX, where they formerly were never found. It's very possible that they will gradually become a more common breeder here (and also possible they will become less common in the hotter parts of their range as high end temperature increases there) as climate change shifts temp/precipitation norms.
Finally, plenty of species successfully colonize areas that they didn't originally evolve in, and aren't 'adapted to' in an evolutionary sense. Many of the species seen in the cities of the Great Plains would historically not have occurred here at all or in the numbers that they do now unless we had created artificial 'forests' throughout the area, which we did by pumping masses of groundwater from the rapidly depleting Ogallala Aquifer. Examples of common species in my backyard that would not have historically been common here (that is, they didn't evolve here and wouldn't typically occur here without humans altering the environment) would be blue jays (not enough mast material without oaks/pecans), cardinals (same), wintering geese and cranes (use human sorghum and wheat fields in the winter), gray tree squirrels (few trees on the plains, historically), kestrels (need cavities in mature large trees to nest), Mississippi kites (need tall canopy trees to nest), white-winged doves (strongly associated with human development), house sparrows (ditto), Eurasian collared doves (ditto), great tailed grackles (ditto). Most of these species appeared on the Great Plains in the 1960s and 1970s, when the trees planted during the founding of the cities began to mature. They would not have viable populations in this region without trees and water provided by humans, b/c they are not well-adapted (evolutionarily) to landscape and conditions outside the cities.
Conversely, species that are well-adapted evolutionarily to the conditions here (e.g., Lesser Prairie-Chickens) are getting in increasing trouble as climate change bumps the regional temps to even just a few degrees hotter, and the ambient humidity a few points lower. Hen chickens have a limited tolerance for high temps, and their eggs have limited tolerance for low humidity. Hens might tolerate, e.g., 103 F at ground level for a few hours every day at midday during incubation and brooding, but 106 F might cause her to abandon. So while P-Chickens evolved in conditions where heat spikes might have historically occurred every third or fourth year, such conditions were still infrequent enough for reproductive success to sustain the population. But as we've (for example) seen frequency of extreme droughts or extreme heat spikes increase, then years of complete reproductive failure become more common and the Prairie-Chicken eventually might be extirpated (even though they evolved in this area originally).
Yikes, I didn't mean to write that much. Just got going, and...
