Population trend Clause Samples

Population trend. Trend analyses were run in TRIM software using the linear trend model with stepwise selection of change points (missing values removed) with serial correlation taken into account but not overdispersion. The multiplicative overall slope estimate in TRIM is converted into one of the following categories. The category depends on the overall slope as well as its 95% confidence interval (= slope +/- 1.96 times the standard error of the slope).

Population trend. Declining. This is probably primarily due to the high human population densities and transformation of suitable habitat to agriculture and other land uses.

Population trend. The Grey Crowned Crane population in Tanzania has and continues to decline significantly. This decline is attributed to habitat degradation, mining, poisoning and the captive trade market.

Population trend. Description of the direction and rate of change in population size (i.e. trend) is the other fundamental attribute used to assess the status of a species or population at site, national or flyway scales. However, both the length of the trend period and the trend classification depends on the purpose of the analysis and data availability. Ideally, trends are based on annual data for better statistical power, but less frequent (ideally not less frequent than once in every 3 years) data collection might be acceptable if establishing the trend would require very extensive surveys. Trend periods can be: i. A fixed moving time period (typically the last 5, 10 or 25 years) used to characterise the current (i.e. most recent short-term) or long-term trend. The current trends can be used as an early warning, while the long-term trends are less influenced by short-term fluctuations. This makes them more robust but also less sensitive. The long-term trend could indicate a problem too late if a population for example recovered at some point in the time series, but then declined again. ii. Linked to some policy-relevant benchmark, e.g. 1980 is used both for the EU Article 12 reporting as this is the first full year after the Birds Directive came into force. (For the sake of consistency, the same start year has been adopted also for the AEWA national population status reporting). The year of designation of a protected area can be used to assess whether the site still holds the numbers it has been designated for. iii. Linked to generation length, e.g. the trend rend over 10 years or 3 generations, whichever is the longer is used by both the IUCN Red List and for the classification of populations on AEWA Table 1 under the criteria 2c and 3c of Columns A and B respectively. The rate of change is often compared to certain pre-set values, either to classify the trend or to use it in alert or trigger systems based on its value and the width of its confidence intervals.

Population trend. Declining. This is probably primarily due to the high human population densities and transformation of suitable habitat to agriculture and other land uses. Mozambique’s Grey Crowned Crane population has declined from several 1 000 in 1985 to around 250 individuals. The species primarily occurs south of the Zambezi River, in Gorongosa National Park, the Zambezi Delta, and Banhine National Park, and is presumed to be the southern Africa sub-species. The status of the northern Mozambique population, in and around Niassa National Park, is unknown. The Grey Crowned Crane population in Mozambique appears to stable in central Mozambique, and is possibly in decline elsewhere. Threats likely include reduced water availability due to large dams and water diversions, uncontrolled fires, and (unconfirmed) egg and chick theft. The current Namibian population stands at less than 20 birds, down from an estimated 100 individuals in 1985. Similar to Botswana, the species is not considered a resident population, but rather that scattered individuals visit the country during ideal conditions.

Population trend. The Grey Crowned Crane population in Tanzania has and continues to decline significantly. This decline is attributed to habitat degradation, mining, poisoning and the captive trade market. From an estimated population of 35 000 in 1985, the species has declined to a current level of between 6 500 and 8 000 individuals. Although widespread across south-western, southern and south-eastern parts of the country, they are concentrated in the Mbarara / Bushenyi, Masaka and Kabale Regions in the south-western parts of the country. Grey Crowned Cranes have declined by up to 80% over the past 40 years in the country. This has been attributed to habitat loss, capture of cranes for the captive trade markets and human disturbance around nesting sites, resulting in lower breeding productivity.

Population trend. The species is increasing in the country, with an estimated 44% increase between 2001 and 2012. However, threats to the species include habitat loss, the illegal removal of birds for the captive trade market, collisions on overhead wires, electrocutions on electrical infrastructure and poisoning. Grey Crowned Cranes have only recently been recorded in South Sudan and are most likely birds from Uganda moving north along the Nile River as far north as Juba (Dodman pers.comm.)