July 14, 2014 by Rokman61
By the end of May nearly all the summer residents have arrived and most songbirds are preoccupied with the business of propagation: claiming and defending territory, nest-building, and feeding young. You can see from the shape of its stout conical bill that this White-crowned Sparrow is predominantly a seed-eater. Interestingly, many vegetarian songbirds like this one switch their diet to invertebrates when feeding their nestlings. By contrast, warblers such as this Common Yellowthroat are virtually obligate insectivores, so insects are the expected fare for nurturing their young. A closer view of a proud and very busy momma. .
Purple Martins are large handsome swallows that were once common across the continent. The eastern populations have experienced a major crash, and the west coast population was essentially extirpated from BC by about 1980 – their natural habitat having largely been replaced by urban development. It was discovered that they readily took to artificial nesting boxes placed on pilings along tidal shores. Volunteers have been installing suitable nest boxes at appropriate locations. Because of this program, Martins from father south have gradually spread northward, hence the population in the BC Lower Mainland has gone from zero to hundreds of nesting pairs. At a time when most songbirds are in decline, this ranks as an outstanding success story. The birds are colonial nesters, so dense clusters of boxes are just what they want. Here is a typical example from the Fraser estuary. The male birds are completely iridescent blue/purple, whilst the females are pale grey on the undersides. Near their nesting colonies the birds are delightfully vocal, constantly chortling as they swoop around the nest boxes. Occasionally groups of them will alight in nearby trees, which explains how I was lucky enough to get these images. There are six birds in this one little cluster. Martins are strong flyers and will go long distances to forage – we occasionally hear them high above our yard. Recently it was discovered that our western birds migrate all the way to Brazil to spend the winter.
Of course all the nesting activity produces many newly-fledged birds. This young Downy Woodpecker appeared in our yard on one rainy day, looking a bit damp and dishevelled. A few more miscellaneous birds:
Bald Eagles are undoubtedly the most photographed bird in BC. Nonetheless I thought this opportunity was too good to pass up. This individual was in the process of drying out after a rainy morning. I took a few shots, and minutes later we were both doused by a heavy squall. In contrast, here is a fairly common bird that is a challenge to see, let alone get a decent photograph of, which I have yet to manage. Although the Red-eyed Vireo tends to sing non-stop, it usually does so buried in the canopy of tall trees. If one gets any view, it is most often of the bottom of the bird, as in this photograph. The pale belly can be about the same colour as the sky above, and the mantle of the bird blends with leaves it hides among.
A defunct WW II housing development near Boundary Bay is now a community park, where the various trees once used for landscaping are an interesting attraction. Several ornamental poplar trees (Populus sp) have cloned themselves into rather large groves. They are tall trees with leaves that are very silvery on the undersides, but when newly-formed they look like this. These poplars must be particularly attractive to caterpillars, as it seems that they get defoliated during outbreaks fairly often. One day I came upon a near blizzard of white objects flitting around in the poplar canopy. Here is a close view of one of the fliers – a White Satin Moth, quite a handsome critter. This moth is an introduced species which apparently specializes in poplar and willow hosts. Judging by their shear abundance, the poplar groves will soon experience yet another defoliation event.
Also present in the old housing area are rows of horse-chestnut trees that were planted to provide shade along the streets. Here is a cluster of immature fruits – and the answer to the ‘mystery photo’. These are not edible chestnuts, and are not even closely related to real chestnuts of the genus Castanea. They belong to the genus Aesculus, several species of which are native to North America and are known as ‘buckeyes’ – a much more suitable name in my opinion.
A few more miscellaneous creatures.
This little guy is a young Eastern Cottontail, an introduced species that is seasonally rather common in the Lower Mainland. On one early morning walk I encountered about a dozen of them, and this very young individual elected not to scurry away upon my approach. I reached down, gently picked it up, took this selfie, put it back, and watched as it leisurely hopped off into tall grass – as if nothing untoward had happened to it. As a youngster I kept a few pet bunnies that were never so cooperative.
Disclaimer: No vertebrates (birds, mammals, or reptiles) were harmed in any way for the production of this blog posting. However, some botanical materials (berries) were consumed, and quite a few arthropods (mosquitoes) met an untimely end.
Last summer I had occasion to spend a few days in Salmon Arm (see blog for June-July, 2013), and the opportunity came up again this year. I got almost no photos of wildlife to present here, but the flowers were very much worth noting. Orange seemed to be the colour of the season.
And a yellow one:
The rest of this blog is about things of geologic nature. Lithophobes (rock haters) may want to stop here.
A friend told me about an interesting geologic feature referred to as the “Devil’s Woodpile”. From the name it was obviously going to be an outcrop of columnar lava rocks, always worth a look. On my way to Salmon Arm, I followed the directions provided, arrived at the site, and clattered up the talus to the base of the cliff, which looked like this. Following along the base of the cliff, the orientation of the columns abruptly changed so that the columns were lying sideways.- now one can see why the featured got its name. Columns form when a mass of lava solidifies and shrinks as it cools. A regular pattern of cracks develop, much like shrinkage cracks in drying mud. The cracks propagate down, resulting in the columnar shapes. Since the columns ‘grow’ at right angles to the cooling surfaces, they indicate the shape and orientation of the lava body. In this example, the nearly vertical columns must have formed in a horizontal sheet of lava, whereas the nearly horizontal columns would have formed (cooled) against a steep surface. From this we can interpret that the lava flowed into and filled a ravine or gully with an abrupt steep margin. In the image below, the change in orientation is visible by the curving and fanning columns to the left of the base of the tree (yellow lines). (Click to enlarge for a clearer view).
The region around Salmon Arm and Shuswap Lake is geologically famous for its ‘Shuswap Gneiss’, a complex of highly metamorphosed rocks that have been studied extensively for well over a hundred years. Here is a photo of an outcrop that would get any hard rock geologist salivating. I will point out below some of the features that can be observed in this image. (Click to enlarge for more detail). First note that there are essentially two different rock types present. The thin, dark/light layers are a rock known as gneiss, a metamorphic rock characterized by nicely banded structure, and in this case numerous folds (yellow-green lines in photo below – enlarge if you don’t see them clearly). The thick band of pale rock across the lower field of view has a very lumpy-looking appearance, due to the big white things that are large single crystals of feldspar (red ‘F‘s in photo below). This rock is pegmatite, a very coarse and irregularly-textured form of granite. A small fault (a surface along which the rocks have slipped) cuts through and displaces the pegmatite and gneiss (red lines in middle of image).
Gneisses are highly metamorphosed rocks, and these particular ones are possibly part of the ancient core of the North American continent, more than a thousand million years old. They were once deeply buried under very thick layers of younger deposits. In the complicated tectonic processes that lead to the building of the western mountain ranges, the rocks in the photo were first forced still deeper (15-25 km), then brought back to the surface when part of their cover slid off. At the extreme depths at which these rocks were subjected, temperatures reach 100’s C, the overlying rocks apply enormous pressure, and rocks do not behave as they do at the surface. Instead of being strong and brittle like glass, they become soft and ductile like putty, slowly changing shape in response to applied pressure. The high temperatures cause certain constituents in the rocks to melt and segregate into pockets of granitic composition – the pegmatite seen here. Intense unequal pressure also causes the rock mass to flow and flatten into parallel orientation as evident in the photo. Layers that are caught at angles to the directed pressure are folded (bent back on themselves), as evident in this outcrop (yellow-green lines). The small fault is a much later feature, representing some minor adjustments that took place as the rocks rose to higher and cooler levels.
I could continue, but probably have presented more than most would want, so perhaps a good place to stop.
Carlo, aka Rokman61