Causes of change

Demographic trends in breeding parameters do not suggest that increases in this species are due to improvements in breeding performance. There is some evidence, albeit limited, that improvements in survival rates, due to amelioration in wintering conditions, may have been responsible. Evidence for ecological drivers of the population increase is limited but increased provisioning in gardens and milder winters may have played a role.

Further information on causes of change

The number of fledglings per breeding attempt have decreased alongside decreases in clutch and brood sizes (see above). Daily failure rates at the egg stage have also decreased but daily failure rates at the chick stage has not changed. Consequently, breeding success does not contribute substantially to population change, and integrated modelling confirms that variation in adult survival is the primary driver of annual population change (Robinson et al. 2014).

Increases in survival rates, due to more widespread food provision in gardens during winter is one possible explanation for the increase (Plummer et al. 2019). Horak & Lebreton (1998) found that survival rates in Estonia were higher in urban populations than rural ones and suggested that this was partly due to supplementary feeding in gardens. Increasing winter temperature may have also played a role. Ahola et al. (2009) suggested that, for their study population in Sweden, increasingly favourable conditions in winters have enhanced the survival rates of Great Tit and resulted in the observed increase in Great Tit breeding density.

Other factors are also likely to influence survival rates. There is some evidence that the beech crop may be influential and it has been shown that survival rates can be related to beechmast production (Verhulst 1992, Perdeck et al. 2000), although there is no evidence that beechmast production has gone up. Perdeck et al. (2000) provided further evidence for this as supplemental food increased survival of both juveniles and adults, supporting the winter-food limitation hypothesis. In a Finnish population, Orell (1989) reported that the high survival rates of resident juveniles after a warm August may be attributable to food availability during the time when the birds undergo their post-juvenile moult.

Great Tits have advanced their laying date, in line with climatic change. This has been found by several studies (e.g. Sanz 2002, Visser et al. 2009, Bauer et al. 2010), but does not seem to be influencing the population trend. Intraspecific competition may also drive population changes in Great tits (Gamelon et al. 2019), and there is evidence that density-dependent effects influence clutch size, hatching success and fledging success, which may explain the decreases observed in clutch size as fledging rates as the population has increased (Bodey et al. 2020). Severe weather events are expected to become more frequent as a result of climate change and conditions such as heavy and persistent rainfall can also be an important driver of Great Tit breeding success (Scholl et al. 2020); however, there is no evidence that this has driven population change.

Information about conservation actions

Like its close relative the Blue Tit, the population of this species has increased since the 1970s, hence it is not a species of concern and no conservation actions are currently required. However, it has experienced a shallow decline over the last ten years and therefore ongoing monitoring would be prudent.

Ongoing provision of garden bird food is likely to continue to benefit the Great Tit. However, the effects are not always entirely positive and feeders may contribute to the spread of avian pox, so those providing food should ensure they follow good hygiene practices. The provision of nest boxes, both in gardens and elsewhere, is also likely to continue to benefit this species.