This figure shows the total number of nests per species in Wytham Woods in spring 2021. The inner shaded column indicates the number of nests where at least one chick successfully fledged. Approxiamtely 70% of Blue tit nests were successful in fledging at least one chick, whereas only 63% of our great tit nests produced any fledglings.

This figure shows the mean number of chicks that hatched in each nest and for each species. The inner shaded column shows the mean number of chicks that fledged from each nest for each species, where that nest had at least one chick that hatched.For blue tits, on average, approximately 78% of chicks survived in each nest, whereas for great tits this was slightly lower at approximately 73%.

This figure shows the data for the mean clutch size of great tit nests from 1960 to 2021*. The mean clutch size for great tits in 2021 was 7.2 eggs (highlighted in red), only 2016 (6.6 eggs) and 2013 (6.7 eggs) have been lower in recent years.

* Data from 2020 missing

Here we see how the mean lay date for great tits varied across Wytham Woods. The dark blue spot in the centre of the graph is the mean lay date for the entire wood, the light blue dot is the lay date for each section of the woods. There are 3 areas in the wood that were earlier than the mean, those were Marley Plantation and Bean in the south and Great Wood in the north.

Egg laying Map

This map shows how egg laying advanced througout the wood during April and May. The areas to the south (Bean by Eynsham Road and Marley Plantation by the Botley Interchange) and far north (Great Wood bordering the Thames) were earliest. This is not surprising when considering the areas to the south, but why is Great Wood in the north also early? In general areas around the edge of the wood lay earliest but also areas of low lying land, Great Wood is one lowest parts of the wood.

This figure shows how the mean hatch date for great tits has advanced in time since 1960. In the 1960s the mean hatch date was around April day 52 (22nd of May). In the 1970s it stayed around the same day but had started to become earlier by the 1980s, falling to April day 48 (18th of May) by the beginning of the ’90s.

If we look a bit more closely at mean hatch dates since the year 2000, we can see that recently the date has ranged from April day 35 up as high as April day 54 which is between the 5th and 24th of May.The average for this entire period is approximately April Day 42, and for 2021 it was just slightly later than that, coming in around April day 44 (14th of May).