The Gran Canaria Blue Chaffinch Fringilla polatzeki is a threatened, endemic, forest‐dwelling bird species of the Canary Islands, whose core population at the end of the 20th century was restricted to the pine forests of Inagua Nature Reserve (38 km2). A translocation programme released birds from a breeding centre into the nearby (<3 km) pine forests of La Cumbre in the years following 2010. From 2015 to 2019 the La Cumbre population was reinforced by translocation of wild juveniles from the source population of Inagua. We estimate the population size, the spatial variation of abundance, and recent temporal changes in density of the species in Inagua and La Cumbre by means of line transects, distance sampling, and habitat suitability modelling using random forests. The average density of the Blue Chaffinch in Inagua Nature Reserve was 10.2 birds/km2 in spring 2019, with a population estimated at 362 birds (95% CI: 257–489). The most important variables affecting the distribution of the Blue Chaffinch in Inagua were the amount of precipitation during the summer (July–September), the solar radiation in June, and the northern position in the reserve, highlighting the importance of abiotic factors related to thermal and hydric stress during the breeding season. The density was considerably lower in the translocated population inhabiting 21 km2 of pine forests in La Cumbre (3.3 birds/km2), with an estimate of 68 Blue Chaffinches (35–141) breeding freely in the wild. The translocation programme successfully contributed to the establishment of a second viable nucleus, accounting for 16% of the total population within a time span of 10 years. This result reinforces the role of translocations in preventing extinctions of endangered species with very low population sizes restricted to only one isolated area.

大加那利岛蓝燕雀 Fringilla polatzeki是加那利群岛的一种受威胁的地方性森林栖息鸟类，其核心种群在 20 世纪末仅限于 Inagua 自然保护区的松树林（38 km 2）。在 2010 年之后的几年里，一项易地计划将鸟类从繁殖中心释放到附近（<3 公里）的 La Cumbre 松树林中。从 2015 年到 2019 年，La Cumbre 种群通过从 Inagua 源种群中转移野生幼鸟而得到加强。我们通过线样断面、距离采样和使用随机森林的栖息地适宜性建模来估计 Inagua 和 La Cumbre 的种群规模、丰度的空间变化和最近物种密度的时间变化。Inagua 自然保护区蓝燕雀的平均密度为 10.2 只/km 22019 年春季，估计种群数量为 362 只（95% CI：257-489）。影响 Inagua 蓝燕雀分布的最重要变量是夏季（7 月至 9 月）的降水量、6 月的太阳辐射和保护区的北部位置，突出了与热相关的非生物因素的重要性和繁殖季节的水分胁迫。居住在 La Cumbre 21 km 2松林中的易地种群的密度要低得多（3.3 只鸟/km 2)，估计有 68 只蓝燕雀 (35–141) 在野外自由繁殖。易位计划成功促成了第二个可行核心的建立，在 10 年的时间跨度内占总人口的 16%。这一结果加强了易位在防止濒危物种灭绝方面的作用，这些物种的种群数量非常少，仅限于一个孤立的区域。