1 INTRODUCTION

The grey parrot has been among the most frequently traded of all bird species listed under CITES (Martin, 2018). Due to drastic negative population trends, it was recently uplisted to ‘Endangered’ on the IUCN Red List and transferred to CITES Appendix I (BirdLife International, 2020; CITES, 2016).

A major threat to the grey parrot is the intensive harvest for the pet trade. Between 1975 and 2018, more than 1.4 Mio individuals of wild grey parrots (grey parrot Psittacus erithacus and the former subspecies timneh parrot (now Psittacus timneh) were reported as having been exported from range states (UNEP World Conservation Monitoring Centre, 2020), with actual offtake being much higher due to pre-export mortality (CITES, 2016; Fotso, 1998a, 1998b; McGowan, 2001) and nondocumented illegal harvest (Martin, Perrin, et al., 2014). Another threat mentioned has been overall habitat loss and removal of important breeding trees (Annorbah et al., 2016; Martin, Perrin, et al., 2014), but there is also evidence that traditional agricultural landscapes and even towns can be suitable for feeding and breeding (Düker et al., 2020). The impact of the occasional use of grey parrots as bushmeat or for ceremonial and medical purposes is less clear (Düker et al., 2020; Fa et al., 2006).

Significant population declines of grey parrots are documented from across their range (Martin, Perrin, et al., 2014). BirdLife International (2020) estimated a population decline of 50%–79% in the last three generations (47 years). Ghana lost 90%–99% of its population since 1992 (Annorbah et al., 2016), and even back then, populations were considered to have been already drastically reduced (Dändliker, 1992). There are also hints for serious declines in Nigeria, Uganda, Kenya and other African countries (Hart et al., 2016; Martin, Perrin, et al., 2014; McGowan, 2001).

Cameroon's population was estimated at 300,000–500,000 individuals in 1996 and 1997 (Fotso, 1998b) and at ca. 200,000 birds in 2008–2011 (Tamungang & Cheke, 2012; Tamungang et al., 2013). Both of these estimates have been criticised for their methodology (Martin, Gilardi, et al., 2014; Martin, Perrin, et al., 2014; McGowan, 2001), but a strong population decline is likely and would be in line with assessments by other field biologists (Martin, Perrin, et al., 2014). However, the possibilities to quantify such trends are rare and every opportunity to get more information about population developments is extremely valuable.

The Korup area in Southwest Cameroon with its largely unfragmented forests and traditional smallholder mosaic landscapes still provide important habitat for grey parrot populations (Düker et al., 2020; Kupsch et al., 2019). Density estimates from south of Korup National Park for 2016 suggest a strong decline in a period of 6–8 years (Düker et al., 2020; Tamungang et al., 2016). However, the methods used to calculate population densities in these surveys differed, thus preventing strong conclusions about population trends in the region.

In this study, we present line transect data from two more sites around Korup National Park from 2001/2002 and 2016. These surveys were conducted as multispecies surveys targeting mainly primates and large birds (Waltert et al., 2002) and used an exact same methodology and largely the same observers. This gives an extremely valuable opportunity to reliably quantify abundance trends based on historical baseline data and a repeated survey 14/15 years later, which is approximately the estimated generation length of grey parrots (15.5 years) (Bird et al., 2020; BirdLife International, 2020). Based on other surveys from the region and the global population trend, we also expected a strong decrease in encounter rates and density in this time period.

中文翻译：

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确认2002年至2016年期间喀麦隆Korup地区的灰鹦鹉数量大幅下降

1引言

灰鹦鹉一直是《濒危野生动植物种国际贸易公约》（CITES ）所列所有鸟类中交易最频繁的物种之一（Martin，  2018）由于人口急剧下降的趋势，该物种最近在IUCN红色名录中被列为“濒危物种”，并被转移到CITES附录I（BirdLife International，  2020； CITES，  2016）。

灰鹦鹉的主要威胁是宠物贸易的密集收获。在1975年至2018年之间，据报道有超过1.4 Mio的野生灰鹦鹉（灰鹦鹉Psittacus erithacus和以前的亚种timneh鹦鹉（现在的Psittacus timneh））是从各州出口的（UNEP世界自然保护监测中心，  2020年）。由于出口前的死亡率（CITES，  2016 ; Fotso，  1998a，1998b ; McGowan，2001）和无证非法采摘（Martin，Perrin等，2014），实际的采伐量要高 得多。 ）。提到的另一个威胁是总体栖息地的丧失和重要育种树的清除（Annorbah等人，  2016年； Martin，Perrin等人，  2014年），但也有证据表明传统的农业景观甚至城镇都适合饲养和育种（Düker等，  2020）。偶尔使用灰鹦鹉作为食用森林猎物或用于礼仪和医疗目的的影响尚不清楚（Düker等人，  2020年； Fa等人，  2006年）。

灰鹦鹉的种群数量在整个范围内都有显着下降（Martin，Perrin等，  2014）。鸟类保护国际组织（2020年）估计，最近三代（47岁）的人口下降了50％至79％。自1992年以来，加纳丧失了90％至99％的人口（Annorbah等人，  2016年），即使在那时候，也被认为人口已经急剧减少（Dändliker，  1992年）。还有迹象表明，尼日利亚，乌干达，肯尼亚和其他非洲国家将出现严重下降（Hart等人，  2016年； Martin，Perrin等人，  2014年； McGowan，  2001年）。

喀麦隆的人口在1996年和1997年估计为300,000-500,000人（Fotso，  1998b），大约在2000年。2008-2011年有20万只鸟（Tamungang＆Cheke，  2012 ; Tamungang et al。，  2013）。这两种估计都因其方法论而受到批评（Martin，Gilardi等，  2014； Martin，Perrin等，  2014； McGowan，  2001），但是人口的下降很可能而且将与评估相符。其他野外生物学家（Martin，Perrin，et al。，  2014）。但是，量化这种趋势的可能性很少，而且每一个获得更多有关人口发展信息的机会都是非常宝贵的。

喀麦隆西南部的科鲁普（Korup）地区基本上没有碎片森林和传统的小农户马赛克景观，仍然为灰鹦鹉种群提供了重要的栖息地（Düker等人，  2020年; Kupsch等人，  2019年）。2016年库鲁普国家公园以南的密度估计值表明，在6至8年的时间里下降幅度很大（Düker等，  2020； Tamungang等，  2016）。但是，这些调查中用于计算人口密度的方法各不相同，因此无法得出有关该地区人口趋势的强有力结论。

在这项研究中，我们提供了2001/2002和2016年来自库鲁普国家公园附近两个地点的线样数据。这些调查是针对主要灵长类和大型鸟类的多物种调查（Waltert等人，  2002），并使用了完全相同的方法方法论和大致相同的观察者。这为基于历史基线数据和14/15年后的重复调查可靠地量化丰度趋势提供了极为宝贵的机会，这大约是灰鹦鹉的估计世代长度（15.5年）（Bird等人，  2020； BirdLife International ，  2020年）。根据来自该地区的其他调查以及全球人口趋势，我们还预计在此期间遭遇率和密度将大大降低。