Great tits in Britain are now laying their eggs two weeks earlier than they did 60 years ago because of climate change, study finds 

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  • Researchers track 13,000 great breasts over a 60-year period in Oxfordshire
  • Birds nesting more than two weeks earlier than study began
  • This is in part due to the leaves on nearby oak trees emerging before they are warm.
  • This leads to the caterpillars that the birds feed on when they first emerge in the spring.
  • There is a risk that the birds are not nesting early enough to adjust to the food sources

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Great tits are laying their eggs up to a fortnight earlier than they did 60 years ago, according to a new study that found it to be a result of climate change.

To examine the impact of global warming on birds, the researchers used breeding data from more than 13,000 great tits tracked over a 60-year period in Oxfordshire.

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The earlier occurrence of spring as a result of warmer temperatures and climate change requires populations of plants and animals to change the timing of life events – such as reproduction – to keep pace with more suitable conditions.

The team from the University of Oxford found that, on average, birds were laying eggs 16.2 days before the start of the study, up from about 25.6 days earlier.

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Great tits are laying their eggs up to a fortnight earlier than they did 60 years ago, according to a new study that found it to be a result of climate change. stock image

Paris Agreement: Agreement to limit the rise in temperature

The Paris Agreement, first signed in 2015, is an international agreement to control and limit climate change.

It hopes to step up efforts to keep the increase in global mean temperature below 2 °C (3.6 °F) and limit temperature rise to 1.5 °C (2.7 °F).

It looks like the more ambitious goal of limiting global warming to 1.5 °C (2.7 °F) may be more important than ever, according to previous research, which claims that 25 percent of the world’s drought conditions will be significantly reduced. can see the increase.

The Paris Agreement on Climate Change has four main goals with respect to reducing emissions:

1) Long-term goal of keeping the increase in global mean temperature below 2 °C above pre-industrial levels

2) Aim to limit the increase to 1.5 °C, as this will significantly reduce the risks and effects of climate change

3) Governments agreed on the need to peak global emissions as quickly as possible, recognizing that this will take longer for developing countries

4) then sharply cut according to the best available science

Source: European Commission

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As temperatures are rising in spring and summer due to climate change, some species are flowering, laying eggs or appearing earlier in the year.

Great tits (Pars major) belong to a well-studied food-web, in which these songbirds feed on caterpillars, which in turn feed on newly emerged oak leaves.

Hot springs are linked to the timing of life events for all three of the earlier events.

But the caterpillars and oak leaves are moving faster than the birds first, putting the big tits at risk of synchronizing with their food source.

Lead author, Charlotte Regan, and her colleagues examined data from birds collected between 1961 and 2020.

This information was collected on great tits living and nesting in 385-hectares of woodland in Oxfordshire.

They found that there was small-scale variation in egg-laying time by larger breasts that could not be revealed by population-scale analysis alone.

The great tit population at Witham Woods near Oxford has been studied intensively for more than six decades.

They used this data to look for temporal and spatial changes in breeding times as the climate changed.

‘When we consider complete population data between 1961 and 2020, the date of female laying and the annual timing of peak abundance of winter insect larvae increased by more than two weeks,’ the authors wrote.

Notably, the laying date progressed by an average of 16.2 days in the population as a whole during the study.

However, at the level of the individual nest box, the breeding dates of females vary greatly.

This occurred 7.5 to 25.6 days earlier than the start of the study.

‘Furthermore, a significant predictor of variability in laying date was the health of oak trees located within 75 m of each nest box,’ the team found.

‘For example, birds that breed in boxes surrounded by healthy oaks improve their laying by 0.34 days per year, while those nesting in areas of poor health improve their laying by only 0.25 days per year.’

Healthy oaks, and in turn caterpillars that eat from oak leaves, are slow birds that proceed to lay their eggs later in the year.

‘Oak trees are an extremely important component of tit foraging habitat because the caterpillars on oak foliage are at their highest density,’ they wrote.

‘Great tits that breed in oak-rich areas breed earlier and have higher reproductive success.’

The authors explain that this research has implications for understanding the ability of organisms to survive under small-scale climate change.

The earlier occurrence of spring as a result of warmer temperatures and climate change requires populations of plants and animals to change the timing of life events – such as reproduction – to keep pace with more suitable conditions.  stock image

The earlier occurrence of spring as a result of warmer temperatures and climate change requires populations of plants and animals to change the timing of life events – such as reproduction – to keep pace with more suitable conditions. stock image

They argue that climate change responses need to be assessed in terms of complex and local selective factors, not just taking averages.

Studying changes in the timing of biological events and resource use on an individual scale ‘can provide new insights into the processes and constraints’ that govern how animals adapt to a changing environment, they wrote.

‘Further work should test how phenological change varies in different systems at different spatial scales and explore both the underlying mechanisms and the ecological and evolutionary consequences of these processes.’

The conclusion has been published in …

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