12 research outputs found
Influence of pasture type and supplement on fertility and liveweight of cows, and progeny growth rate in the dry tropics of northern Queensland
Effects of weaning and supplementation on performance of Brahman cross cows and their progeny
Something for the weekend? Examining the bias in avian phenological recording
In this paper we examine the bias towards
weekend recording (the weekend effect) in volunteer
phenology, using over 14,000 bird migration phenological
observations from eight locations in the UK as a data
source. Data from 45 bird species were used. Overall, 44%
of all records were taken at weekends in contrast to the
28.6% (i.e. two out of seven days) that would be expected
if records were evenly spread throughout the week. Whilst
there is documented evidence of environmental differences
at weekends, particularly in large urban areas, we believe
the weekend effect is mostly a consequence of greater
recorder effort at weekends. Some birds, likely to be
obvious by their behaviour or abundance, had fewer
weekend records than the remaining species. The weekend
effect, to some extent, differed between locations and
between seasons. There was some evidence that, particularly
in autumn, the weekend bias may be lessening. If so,
this will increase the accuracy of phenological records,
making the detection of changes and responses to temperature
easier
How consistent are trends in arrival (and departure) dates of migrant birds in the UK?
We examine the first arrival and last departure dates of migrant bird species from, respectively, six and three English area bird reports. Of all 145 bird series, 50% demonstrated significantly earlier arrival in recent years with the average advance over all species being 0.25 days/year or 12 days earlier over 50 years. 30% of 67 series demonstrated significantly later departure, with the average species delay being 0.16 days/year or 8 days later over 50 years. There was greater consistency between species in trends in first arrival than in last departure, with species such as sand martin Riparia riparia significantly earlier at all six sites while, for example, spotted flycatcher Muscicapa striata showed no significant change in arrival at all sites. Significant negative correlations between arrival dates and English temperatures were found for 26% of all series but temperature effects on departures were less clear. We provide some evidence that trends in arrival dates may be masked by population declines in birds. Since migrant bird populations are in decline generally this may suggest that the real advance in arrival dates may be greater than that reported here