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The long-term trends in abundance, survival and breeding success generated by these schemes are presented on the BirdTrends webs. All of the data presented here are collected by BTO volunteer ringers and nest recorders and we are extremely grateful for their efforts, both in collecting the data and submitting it promptly.
As their effort is standardised annually, the of birds caught in each year provides an accurate measure of changes in abundance. Recaptures of birds ringed in years also allow survival rates to be calculated. The timing of nesting and the of fledglings reared during each breeding attempt is monitored by over participants in the Nest Record Scheme NRSeach of whom locates nests to count the eggs and young inside at breeding season 6.1 intervals.
The ratio of juvenile to adult birds caught on CESs provides a second measure of breeding success that also takes into the of successful breeding attempts made per adult as many species attempt to rear more than one brood per season and the survival of young birds immediately after fledging.
CES covers 24 woodland, scrub and reedbed species, while NRS covers species breeding across all habitats, from gardens to remote hillsides. Not all of the CES and NRS data collected in have been received yet, so these are based on a subset of sites and species for which we currently hold sufficient data to analyse. Spring started with two named storms bringing wet, windy and unsettled weather in March, particularly in western and northern areas.
By mid-April, the nation was experiencing 20 degree temperatures, followed by another named storm, this time in the south. Despite the varied conditions, overall, spring was slightly warmer than the mean for this period. The start of the CES season was cooler, particularly at night, but the rest of the season was generally warmer than average.
June proved to be a wet month, whereas July was more settled, despite numerous thundery outbreaks breeding season 6.1 in the month. New UK maximum temperature records were set on 29 June and 25 July. The weather in August was more unsettled and showery, with high temperatures later in the month, particularly in the south-east.
The summer was classified as the 12 th warmest and 7 th wettest since CES show that it was a mixed year for migratory warblers. Short-distance migrants Chiffchaff and Blackcap, and the long-distance migrant Whitethroat, were encountered in particularly high s relative to the five-year mean —; Table 1. It is particularly pleasing to see an increase for Whitethroat following ificant declines in every year since ; this increase was predominantly driven by in the east of the country.
Less positively, s of adult Sedge and Reed Warbler in were ificantly lower than the five-year mean. As with Whitethroat, the Reed Warbler were particularly reflective of the situation in the east of the country. Table 1. Adult abundance and breeding success calculated from CES data. Statistically ificant p The biggest winners in were the tits Blue, Great and Long-tailed as well as Treecreeper and Goldfinch Table 1each of which recorded a ificant increase in abundance compared to the five-year mean.
Goldfinch s continue to rise, with the highest ever of adults recorded on CES in ; the four most-abundant years have all occurred in the last five seasons. Treecreeper bounced back from a poor year in and was also recorded in far greater s in than in any year.
Blue Tit was the only species to record a statistically ificant decline in adult survival, suggesting that ificant increase in breeding season 6.1 recorded during was likely to have resulted from high juvenile recruitment following a successful breeding season in Great Tit productivity was also high inwhich is likely to have contributed to the above average s captured on CES this year.
Long-tailed Tit productivity decreased inso the mechanism underpinning the increased abundance recorded in is likely to have been an increase in overwinter survival of juvenile birds, given survival was not ificantly higher than average. The long-term trends — for all five species are positive. The main losers in were species that tend to feed on the ground, with statistically ificant declines in abundance, relative to the five-year mean, recorded for Blackbird, Robin, Dunnock, Chaffinch, Greenfinch and Reed Bunting.
Nine of the lowest abundance years on record have occurred in the past 10 years for Chaffinch, while for Greenfinch, the lowest eight years have occurred in the past 10 seasons. The long-term trends for Blackbird, Dunnock and Reed Bunting also exhibit declines, with that for Reed Bunting being the steepest, s having fallen to the second-lowest on record in ; only Robin demonstrates a positive long-term trend in abundance.
The adult survival rates for Blackbird were the highest on record, and those for Robin, Dunnock and Reed Bunting were also reasonably high, suggesting the decline in abundance was caused by poor recruitment. The decline in Reed Buntings was particularly driven by in the east of the country, whereas for the other species, the declines were more widespread. NRS data indicate that many species bred ificantly earlier in compared with the five-year mean Table 2. For five migrant species, Swallow, Willow Warbler, Blackcap, Pied Flycatcher and Redstart, this resulted in laying dates being between three and five days earlier than average.
While Blackcap experienced the greatest advance, mean Swallow laying dates were the earliest on record, though it should be noticed that, as a multi-brooded species, this could equally reflect a decline in s of broods produced per pair. BirdTrack data indicate that arrival dates for Blackcap were slightly earlier than normal in but no corresponding advance was apparent for the other species exhibiting earlier laying and arrival of Breeding season 6.1 Warbler actually appeared slightly delayed. It is possible that these species took advantage of the warmer-than-average weather in early spring, and mini-heatwave in mid-April, to start breeding earlier than normal.
It is also possible that the wetter-than-average conditions experienced across England and Wales in June in particular, and in Scotland later in the summer reduced their propensity to produce repeat broods, thereby shifting mean laying dates earlier. Only two species, Stock Dove and Barn Owl, exhibited statistically ificant delays in breeding in compared to the five-year mean, laying 18 and 13 days later than average respectively. The warm summer is may have stimulated birds to produce second broods, thus shifting the average laying date later into the year.
Table 2. Laying dates and breeding success calculated from NRS data. Laying dates are given as the of days earlier or later than the five-year average while productivity figures represent a percentage change relative to the five-year average. Statistically ificant p For many species, was an average breeding season, with ificant changes generally suggestive of increased success. CES indicate that for seven species, productivity was ificantly higher than average in Table 1 while NRS data reveal that six species produced above-average s of fledglings per breeding attempt FPBA Table 2.
Chiffchaff was the only migrant species monitored through CES for which productivity was above average across all regions. None of the parameters monitored through NRS e.
Both Pied Flycatcher and Redstart both raised above average s of fledglings per attempt in The first four species, all of which were present in lower s duringare likely to have benefited from reduced competition for resources, allowing remaining pairs to successfully fledge more young. NRS data show that Blue and Great Tits had a particularly successful year, recording statistically ificant increases in clutch and brood size, young-stage survival and therefore in total fledgling production.
The only other species to produce an above-average of fledglings were Tree Pipit breeding season 6.1 Linnet, although it is unclear what the mechanisms underpinning their success were. The only species to exhibit a decrease in productivity on CE Sites was Garden Warbler; the cause of this decline is unclear but it unlikely to be due to density dependence as no ificant increase in abundance was recorded.
CES data indicate that, across all species, productivity was lowest in the west, with fewer species exhibiting statistically ificant increases in productivity in that region. The records used to produce the NRS are generated by over NRS volunteers, who monitor nests ranging from Blue Tit boxes in gardens to seabird colonies on cliffs. If you haven't tried nest recording before, why not give it a go? If you are a qualified ringer with access to an area of scrub, woodland or reedbed where there is the potential to catch at least birds per season, why not register a CES?
Contact the CES Organiser for more information. Constant Effort Sites. How do we monitor the breeding season?
What was the weather like in ? Figure 1.
The Central England Temperature index a indicates that temperatures were above average throughout the season relative to the five-year mean. Share this. The difference we make How you can help Our science Understanding birds Develop your skills. Statistically ificant p Species.Breeding season 6.1
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Non-breeding season habitat quality mediates the strength of density-dependence for a migratory bird