Did the Lower Pecos people live in the rock shelters during the winter and the upland camps during the summers? Why are there two different types of living areas?
Strangely, there is very little hard evidence about seasonality, despite all the materials that have been exhumed from dry rock shelters over the decades. The biggest stumbling block is we can say they WERE there, for example, in the winter and spring, based on food stuffs and cold weather features, but we can't say they WERE NOT here in the summer and fall. It goes back to the old adage "the absence of evidence is not evidence of absence". In Cueva Encantada, a dry rock shelter in Coahuila, we uncovered an infant bed that had been lined with sotol hearts over a layer of heated rocks, obviously an attempt to keep the baby warm, therefore probably wintertime. But there were dozens of other features that could have been built in any season. In Wroe Ranch, in Terrell Co., many of the fiber "nests" were made of grass that retained seed heads - probably summertime - but no way could it be said occupation was only in the summertime and never during the wintertime.
There are a multitude of factors influencing settlement patterns, the main tool used by archeologists to determine where and when people lived as they did. Based on pure common sense, I would think that you sought shelters in the winter and the summer, one for heat and one for shade, with intermittent occupation during inclement weather in spring and fall. One might move out of the shelter because the debris, flies, and stench got to be too oppressive, perhaps someone died and people left to avoid the spirit, food sources had been depleted for some distance around the shelter (and in this include wood for fires), it was time to go meet up with the rest of the family-clan-group somewhere else, Alley-Oop got in a big fight with Lurch over little miss Evening Star and everyone split up to defuse the situation, someone said there is a going to be a communal hunt over at Rattlesnake Canyon next week, the prickly pear harvest was about to begin down on Dog Flats, and I am sick and tired of looking at these three walls and I want to go over to mothers. We can also divide the open camps into two major categories (speaking now about the camps of the Archaic shelter dwellers) - the upland camps that run the gamut from scatters to huge mounds of burned rock, stone tools and debris are often the residue of temporary camps - sometimes used over and over so they grow linearly along the canyons or in increments of burned rock that add up to the huge mounds - but still consisting of several short term occupations. This type of open camp may have been more often created by the foraging or hunting element of the group - folks who were out collecting food and other necessities, cooking up veggie hearts for a couple of days in a midden, hunting deer and rabbit in the fall to whip up those winter robes, building a fish weir, trapping or hunting and drying the catch for transport. Often the use of these camps was scheduled, i.e., the prickly pear harvest had begun on Dog Flats or it was time for the fall deer round up or a huge field of sotol was just about ready to bloom. However, that scheduling may also have depended on other factors of fleeting and temporary nature - for example, I know of two different upland site types that were a response to rainfall on a very immediate basis.
In Terrell County, we did a big block area survey and found extensive open camps (burned rock mounds) at the head of every tributary that had a plunge cavity - a tinaja formed by water cascading off the rim - if the walls were not too steep for easy access. This meant that folks over on the Pecos River could see when rain fell in the uplands and hop right on over there for whatever reason - probably processing a few tons of veggies in the burned rock middens. Two levels of scheduling would have been involved - the general knowledge that it was time to go replenish whatever resource so keep a weather eye to the west and then being prepared to move on moment's notice to take advantage of rainfall. Same reasoning applies to a series of petroglyph open campsites on the high divide to the north where smaller upland tinajas, often consisting of round mortar-like cavities, were capable of holding water for several days after a heavy rain. Limestone lids laying next to the holes indicate that an effort was made to conserve the water for the needs at hand - in this case, probably hunting the various fur and meat bearing animals of the uplands. The petroglyphs suggest the target was deer, with an occasional bison later in time. So the fellows know that the deer will be at their peak in terms of meat and hide quality in the fall and they get ready to move as soon as they know that there is enough water trapped in these reservoirs to sustain them during the harvest. The debris of the two activities is different but both constitute the same type of temporary, sequential open camp. The second type is found along the rivers, especially the Devils, where huge open camps are also composed largely of burned rock and flint with an admixture of shell. These are more likely to be base camps where many of the activities were similar to those carried out in shelters. Here stayed the old and the young while the producing class went out and acquired whatever was needed for everyday life (creating the other type of open camp as they went). Of course, the old and young folks, fished, gathered and hunted what they could as did the whole family while staying by the ever-present water. Rock shelters are much fewer and smaller along the Devils River than along the Pecos or Rio Grande so obviously they were less convenient. The substitute is probably the large open sites at the confluences of canyons and the river. Here I am only trying to contrast shelter and open camp habitation by the same people. Earlier and later, the open camps are more suitable for the needs of mobile hunters, like the folks that followed the bison herds, and for mobile horsemen, like the hostile Plains Indians who avoided the confinement of the canyons and shelters in favor of open grazing and access to water for their horses. There are also camp sites next to big exposures of chert where the raw material for stone tool manufacture was processed to make it easier to lug around and small, isolated hearths atop high hills and canyon rims where the lonely lookout perched, keeping an eye on the horizon (we assume). On the Plains, the latter are often considered to be vision quest sites where the initiate awaits his spirit guide.
Perhaps no aspect of native life is more alien to us than their propensity for moving around, in part because it places severe limitations on private property. The prime mover in the evolutionary process - where we differentiate barbarism (not really a pejorative word you know - my ancestors were all barbarians and they were really quite lovely people) from civilization - is the quality of sedentism - staying put - settling down - building houses - forming villages - instituting bureaucracies - establishing hierarchies - and so on. Sedentism and agricultural go hand in hand, one requires the other.
Voila - the concept of private property - my fields, my crops, my labor, my stocks, my bonds, my car. So let's be glad our people were still moving about, stopping long enough to paint a few walls, and hadn't yet become excruciatingly dull villagers like those I grew up around in Minnesota (although Minnesota is a lovely state and not all of its folks are dull - just look at Jesse Ventura).