Tuesday, April 12, 2011

Tinkerer, Tailor-er, and a Disappearing Nest Maker

It is futile to continue naming favorites. All of the nests in the book, culled from a collection of photographs that leaves at least two dozen waiting in the archives, have their appeal. Some obviously made into print for their builder's inventive use of materials or unusual fabrication techniques. But others were interesting to me because they represent a species facing some survival issues, which was one of the reasons I was compelled to make this book. The not so subtle subtext was to use the nests "as a bower bird lures a mate"  to interesting even a non-birding viewer to learn what might be affecting birds today. 
House Finch, Carpodacus mexicanus, Western Foundation of Vertebrate Zoology
WFVZ Nest 156015
USA: Arizona: Pima County; Tuscon
May 1965 Nest
WFVZ  Eggs 176384  
,California; Riverside County, Hemet
27 July 1989
So in this weeks missive (conveniently borrowing a few paragraphs from the book), for interesting–if not whimsical–nest materials, I offer this thick mix of thread, fabric scraps, and miscellaneous dress trimmings, that also harbors an added twist tie and some crinkly cellophane from a cigarette package. Gathered from what might have been a dress manufacturer's trash bin, and collected in 1965, this haphazard but ambitious assemblage was built by a female House Finch. That she would have tinkered with these modern materials is no surprise:

They brazenly occupy tin cans, old hats, stove pipes, woodpecker holes, cactus, hanging nests of orioles, mud nests of phoebes, street lamps, Christmas wreaths, ivy on buildings—anything which provides solid support and overhanging cover.

Tailorbird, Orthotomus sutorius, Museum of Vertebrate Zoology
MVZ 2347 Nest (larger).
Sri Lanka: Central Province; Galaha, New Forest Estate
04 May 1928
MVZ 2079 Nest (smaller)
Sri Lanka
Date and locality not recorded
In the category of unique building techniques, Common Tailorbirds sometimes pilfer thread, but they put it to use in an entirely different way.

Notorious for loud, metronomic calls that range, depending on their dialect, from annoyingly harsh to melodious, these quick-moving birds are equally famous for a more endearing trait: the talent of “tailoring” live leaves of a shrub together to make a sheltering pouch for their nests. Bending a leaf, or sometimes two, or more, and piercing holes around their edges with their beaks, they insert threads of spiderweb, cocoon silk, plant, or even manmade fibers to hold them in place. They secure these "stitches", as many as two hundred per nest, by fraying the end of the fiber into a rivet-like ball. Tailorbirds living in civilization are famous for brazenly pilfering thread when their human counterparts leave their sewing projects unattended.

Though the male gathers some of the nest materials, the females is the riveter, as well as the mender of monsoon made tears in their leafy shelters.

Loggerhead Shrike, Lanius ludovicianus, Museum of Vertebrate Zoology
MVZ 1653 Nest and Eggs
United States: California: Inyo County; Laws
19 April 1916
And finally, at least for today, I offer this weathered fortress, chosen for the species that constructed it, the Loggerhead Shrike. These big-headed, strong-beaked birds are notorious for impaling their prey on thorns, and sometimes even barbed wire fencing. Despite eating snakes, and controlling rodent and insect infestations, shrikes also eat small birds–a penchant so reviled that a close relative, the Northern Shrike, was shot in the Boston Common to protect House Sparrows, after the introduction of this invasive species in the 1850s.

But persecution isn’t the reason shrikes are missing where they used to be common. Once just found in prairies, sage deserts, scrub, and southern savannahs, their numbers grew when forests were cleared for horse-powered farms and ranches that included grassy pasture and rangeland for good hunting, and shrubs and hedgerows for nesting. But today’s vast acreages of combine-created agriculture and the incursion of sidewalked suburbs have left little untidy wild in which both Loggerhead Shrikes and their prey can thrive. They are virtually absent from the Northeast, and one subspecies in California, the island-bound San Clemente Shrike, is down to fifty pairs. Pesticide use, predation by foxes, cats and crows, along with over grazing of their habitat by farm animals gone feral have all taken their toll, and t
heir use of roadside fence posts as hunting parapets puts them in the lethal path of traffic

It is hard to end this entry with any happy note offering what we might do to save these disappearing birds, but I am not alone in my lament at their decline. Here is an article by one of my favorite local nature writers, Joe Eaton, published in the Berkeley Planet.