Declining bird species are a cause for national concern, and the populations of our winged neighbours have been monitored in long-term studies by the BTO for over forty years. This article describes the ten species with the sharpest observed population declines in the last 25 years, and although some you may never have seen before, others may surprise you. If action to stop these declines isn’t taken soon, we may lose wildlife wonders such as starling murmurations and the haunting cuckoo call.
(25 years -92%) (45 years -95%)
Estimated population size: 14000 territories
Turtle doves have suffered one of the most rapid population declines across Europe in the past few decades, which has been attributed to reduced food availability due to pesticide use, winter mortality due to habitat loss and hunting on their migration route to west Africa.
Identification tip: can be distinguished from Collared doves by their tortoiseshell wings and banded neck pattern.
(25 years -91%) (45 years -92%)
Estimated population size: 3400 pairs (2009)
This red-listed species has become locally extinct in a range of past habitats since the 1970s, and have virtually disappeared from South-East England. The causes of their decline are uncertain, but may be related to woodland deterioration by deer over-grazing and wetland loss due to drainage and drought.
Identification tip: though these small birds are often confused with Marsh tits, the lack of a white spot on their beak gives them away (if you can see it!).
(25 years -85%) (45 years -86%)
Estimated population size: 88,000 pairs (2009)
It appears that the reduced cover of clearfelled forests and newly planted stands increase nest predation and have contributed to the increase in nest failures. A pattern of population decline and tracks indicates that disturbance may also be an issue, and targeted conservation management of undisturbed habitat and preserving mature trees for songposts has been successful.
Vocalisations: A study on Czech populations found that their song repertoires have local dialects.
(25 years: -85%) (45 years: -82%)
Estimated population size: 25,000 pairs
Lesser redpolls thrive with birch populations, and following the felling of trees for the Second World War birch filled the forest gaps left by their slow-growing neighbours, and lesser redpolls flourished until the 1970s. However, as birch were out-competed by their neighbours once more, and pesticides have reduced the weed seeds available, redpoll numbers have plummeted in the last two decades.
Birdbox tip: Nyjer seeds can lure these rare birds into your garden in late winter.
(25 years: -80%) (45 years: -89%)
Estimated population size: 36,000 territories
Although research has found that the population decline seems to arise from a low survival rate in the first year of life, the causes for this mortality are still unknown. Possible causes could be declines in their insect prey, conditions on their wintering grounds or migration routes, and nest predation.
Conservation: Removing nest predators such as squirrels and rats in Leicestershire increased breeding success.
(25 years: -79%) (45 years: -89%)
Estimated population size: 1,900,000 pairs
Although their population has been declining, breeding success has been on the rise for starlings, so it is thought that mortality in the first year of life is the driver of the decline. There is little evidence to conclusively report the cause, but it is thought that changes in livestock farming, pesticide use and farmland drainage has reduced foraging opportunities and food availability.
Vocalisations: Starling song has been known to integrate sounds from their surroundings, including car alarms and human speech patterns.
(25 years: -76%) (45 years: -91%)
Estimated population size: 43,000 territories
Grey partridges appear to be declining due to intensive use of pesticides reducing their insect diet on cereal crops, but the reduction of nesting cover by farmers removing field boundaries and increased predation are also affecting brood survival.
Conservation: Reduced pesticide use and nesting habitats can be provided in shooting estates, but at the cost of controlling predators such as foxes, stoats and weasels.
(25 years: -73%) (45 years: -76%)
Estimated population size: 16,000 pairs
Cuckoo breeding success depends on the nests of their parasitized hosts, and so monitoring their overall success is difficult and varies with different host species and habitats. A cause currently being explored is the possibility that common host birds, such as dunnocks, have been breeding earlier in the season recently, causing mismatch between cuckoos and their hosts.
Evolution: As cuckoos hijack more nests of a species, the species evolve more distinct eggs and better recognition of their eggs, whilst cuckoos evolve to mimic the changing egg patterns, creating an evolutionary arms race.
Lesser spotted woodpecker
(25 years: 73%) (31 years: -60%)
Estimated population size: 1,500 pairs
Reasons for their decline in the UK are unknown, but studies in Europe have found that their presence is strongly associated with dead wood and large deciduous trees. They may also be outcompeted by their bigger cousins, the Great Spotted Woodpeckers.
Spotting: Springtime is the best chance to find them if you look up in open woods, copses, gardens and orchards and listen for their quiet tapping.
(25 years: -63%) (45 years: -73%)
Estimated population size:15,000 territories (2009)
Habitat quality has deteriorated with intensive agricultural practices such as drainage, changes in grazing and cutting regimes and loss of insects associated with cattle, making farmlands less suitable for foraging and breeding.
Namesake: Tail wagging is thought to flush out insect prey and attract mates.