1202 Flash File Bangladesh Krishi

Full text of ' ). To determine whether the rate of population change accelerated or decelerated during the study period, we fitted quadratic Poisson regression models in which both the year and the square of year were included as explanatory variables. The rate of decline is considered decelerating if the regression coefficient for the square of year is positive and is considered accelerating if this coefficient is negative. We carried out significance tests of hypotheses about population changes using F tests, with the ratio of the residual deviance of the model with the most estimated parameters to its residual degrees of freedom being used as the error mean square. Likelihood-ratio tests were not performed because vultures often occur in groups, leading to counts being overdispersed.

The employed population in the primary sector, mainly in agriculture, is gradually. The Bangladesh Development Studies, 7(4), 87-96. The historical evidences in Nepal indicate that prolonged droughts and flash floods have triggered.

For this reason, asymptotic standard errors of parameter estimates are likely to be unreliable, so we obtained 95% confidence intervals for estimates using a bootstrap method. We took random samples of k transects, with replacement, from the k transects available for a particular time period.

We then fitted the regression model for this bootstrap sample and recorded the value of the parameter estimate of interest. This procedure was repeated 1,000 times and the central 950 of the bootstrap estimates were used to define the 95% confidence interval. Further details of log-linear Poisson regression modeling of vulture counts are given by Green etcd. (2004) and Green etal. Crude estimates of vulture population size in 2007 We calculated rough estimates of vulture population size in northern, western, central and north-eastern India by assuming that the transect routes covered a random sample of this region.

In fact, we think that this assumption is incorrect because many routes are located in or near protected areas, but we have ignored this problem in order to obtain crude estimates. We assumed that all vultures within the 1 km-wide recording strip on either side of the transect were detected. Hence, the area in square kilometres covered by a transect is approximately the same as its length in kilometres. We divided the total number of vultures counted on the transects covered in 2007 by their total length in kilometres to obtain an estimate of the number of vultures per square kilometre. We took the total size of the region of northern India within which the surveys were made as being approximately given by that of the states of India, excluding Goa, Andhra Pradesh, Karnataka, Kerala and Tamil Nadu.

Multiplying this area by the vulture densities gives rough estimates of population size. RESULTS Long-term trend in vulture populations Comparison of number of vultures counted on subsets of transects in which the same routes were surveyed in all years indicates very marked declines in numbers over the period 1992-2007 (Table 1).

Numbers of Gyps bengalensis declined by 99.9% between 1992 and 2007 on those transects surveyed in every year during that period. The equivalent 1 Bombay Nat. Soc., 104 (2), May-Aug 2007 129 RECENT CHANGES IN POPULATIONS OF RESIDENT GYPS VULTURES Table 1: Number of vultures counted in each year on comparable sets of road transects in India Species Time period T ransects 1992 2000 2002 2003 2007 G. Bengalensis 1992-2007 70 21,204 888 283 1 - 2007 17 213 180 7 23 2002 - 2007 35 566 37 1 2003 - 2007 10 41 25 G indicus & tenuirostris 1 992 - 2007 70 6,574 17 414 102 213 2000 - 2007 17 223 201 2 - 2007 35 206 8 108 2003 - 2007 10 3 9 G indicus 2002 - 2007 135 812 346 333 2003 - 2007 10 1 4 G tenuirostris 2002 - 2007 135 19 2 2 2003 - 2007 10 2 5 *Each row shows the total number of vultures of a given species recorded in a set of transects covered in all of the survey years within the specified time period decline in the combined total of G.

Software jalan raya. Indicus and G. Tenuirostris was 96.8%. The population indices derived from log-linear Poisson regression models give similar results to those from the simpler approach adopted in Table 1. The population index for Gyps bengalensis in 2007 was 0.

1% of that in 1 992 and the index for G. Indicus and G.

Tenuirostris was 2.6% of the 1992 value (Table 2). Even over the shorter period 2000-2007. The declines have been large.