No abstract

The effect of supplementary food on the reproductive success of Black‐billed Magpies Pica pica was studied in an urban habitat in the city of Edmonton, Alberta, Canada. We provided supplementary food (pelleted dog food) regularly from August 1986 to June 1988 in a feeder situated outside all known magpie territories. Magpies using the supplementary food showed (i) an advancement of 7 days in the initiation of laying, (ii) no increase in clutch‐size, (iii) higher survival of nest contents (eggs and young) during a spring snow storm, (iv) an increase in rate of nestling weight gain, and (v) an increase in fledging success. Supplementary food did not prompt the fed pairs to select nest sites nearer the feeder in 1988 than in 1987. The feeder did not affect the breeding density because the nearest neighbour distances of fed magpies did not differ from unfed magpies in either year, nor did they differ between the two years for either fed or unfed magpies. This study provided evidence that magpies frequently renest even if their initial nests fail after the eggs hatch—a practice that has been reported to be absent or rare in other studies. Although brood reduction was equally frequent in the nests of food‐supplemented and control pairs, the actual number of nestlings disappearing from the former (1.56 per nest) was significantly smaller than that from the latter (2.60 per nest), suggesting that the availability of food plays a major role in magpie reproductive success.

Roadside bird mortality is a new environmental dimension in developing countries. With the recent increase in the number of high-speed cars and the simultaneous improvement of roads in India, bird-car strikes and the resultant bird mortality are becoming important. To know how many species frequent roads in Punjab and thus may be prone to be killed by fast vehicles, we censused birds along 420 km of roads of different widths and traffic volumes from a vehicle moving at 50–60 km per hour. We also counted birds along transects c. 1 km away from roads, for comparison.In all, 35 species of birds were recorded on the road proper or within 3 m of either edge. Common Myna (Acridotheres trisitis) was the most abundant species (34.8% of all birds), followed by House Sparrow (Passer domesticus) (29.5%), Ring Dove (Streptopelia decaocto) (13.1%), and House Crow (Corvus splendens) (9.7%). These four species together accounted for c. 87% of the total of all bird species. The off-road community consisted of 68 species. The species-richness of granivorous, insectivorous, omnivorous, and some other birds, was less on or near roads than in the off-road transects, but within each community, species having different feeding habits were in similar proportions. About 93% of the total birds on or near roads (as against 66% off-road) were either granivorous or omnivorous.Our results suggested that granivorous birds are attracted, but insectivorous and other birds are repelled, by roads. Omnivores were equally abundant on and off roads. Food (such as spilled grain) seemed to be the main factor attracting birds to roads. Species diversity and equitability of the bird community on roads (1.82 and 0.51, respectively) were less than those off-roads (3.11 and 0.74, respectively). Wider roads had lower species-diversity and equitability, probably because of the greater volume of traffic on them compared with narrower roads. Species richness and bird abundance seemed not to be affected by roadwidth. Bird mortality on roads is discussed, along with the possibility of roads acting as “ecological traps” for foraging birds.

House crow damage to sprouting sunflower (Abstract. In an experiment, house crows (Corvus splendens) were estimated to damage 65.1% of sprouting sunflower (Helianthus annuus) seedlings at Ludhiana, Punjab (India). Seed treatments with 0.5% thiram (tetramethylthiuram sulphide) and 0.5% copper oxychloride [3Cu(OH) 2 CuCI 2 ], both commonly used fungicides, did not reduce bird damage. The number of seedlings in a plot from which birds were excluded by netting was significantly greater than, that in any of the chemical treatments as well as in the untreated control.

No abstract

The impact of human disturbance on the choice of trees in which to nest and the heights at which to place the nests by Black-billed Magpies (Pica pica) was studied by comparing nest placement in three areas: A, urban with frequent human disturbance at the nest; B, urban with occasional disturbance; and C, suburban with minimal disturbance. Magpies nested in conifers more frequently than expected, based on availability, in all three areas. Neither absolute nor relative nest height (nest height/tree height) changed over the 2 years of this study, despite frequent human disturbance. The relative nest height did not differ from that 12 years before the current study was initiated. Moreover, nest height (absolute and relative) did not change when 10 pairs renested at new sites in 1987 in area A (after their original nests failed because of a spring snowstorm) even though the original nest sites had been periodically climbed to examine nest contents. Magpies used taller trees in area B than in area A but maintained the same relative nest height, which suggests that they either nested at an optimum height in the trees for ecological reasons or placed their nests as high as they could in the urban environment. Birds in suburban area C nested in shorter trees and at relatively lower levels than those in the urban areas, probably in response to the habitat type. The relative height of magpie nests was significantly greater in urban than in suburban habitat for conifers but not for deciduous trees, this variable being relatively constant within each habitat. Thus, habitat type seemed to have the greatest influence on nest height of magpies, but human disturbance did cause magpies to change trees for renesting in the same season.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. . Wiley and Nordic Society Oikos are collaborating with JSTOR to digitize, preserve and extend access to Ornis Scandinavica. . 1989. The effect of familiarity with an environment on the dominance relationships between juvenile an adult Blackbilled Magpies. -Ornis Scand. 20: 187-192.Dominance status of juvenile and adult Black-billed Magpies Pica pica was studied at a feeding station in the wild and under captive conditions in an outdoor aviary. In the wild, adult magpies won only 15% of 72 interactions recorded at a food source outside any known territory; only adult males were recorded dominating juveniles and then only female juveniles. In captivity, only the dominance status of male magpies was studied. When both age cohorts of males were new to captivity, an adult was top-ranked in only 21% of 24 trials. However, when adult males had > 1 year's residence in capitivity, the dominance relationships changed significantly with adults dominating juveniles in 55% of 22 trials.

Methiocarb (4(methylthio)3,5-xylyl-N-methyl carbamate), a pesticide, and thiram (tetramethylthiuram sulphide), a fungicide, significantly reduced bird damage to sprouting maize (Zea mays) when used as seed dressings at 0.5% a.i. w/w concentration. Statistically, both the treatments were at par though, numerically, thiram appeared better. About 26% of germinating seedlings were estimated to be lost to birds in the untreated control plots. In the laboratory evaluation, no significant effect of the treatments was found on germination percentage, whereas significant reduction in early seedling vigour was recorded with thiram.