Courtesy of an Arctic airflow, April ended on a cold and cloudy note with scattered showers in the south. Despite some rain late in the month, it was England's fourth driest April on record, seeing only 20mm (0.8 in.) of rain; even Scotland had only 35mm, making it their sixth driest. Plenty of sunshine accompanied this dry spell, making April the sunniest on record - 225 hours across the UK as a whole.
The Bank Holiday weekend began bright and sunny with a peppering of heavy showers including some hail and thunder. Despite the sunshine, the Arctic air meant that it remained cold, with highs of only 14C (57F) in eastern England and much of Scotland struggling to get into double figures Celsius. High pressure hung on through Sunday, but a deep area of low pressure then pushed in from the Atlantic, bringing heavy rain and gale force winds across most of the country on Monday - only northern Scotland escaped, with sunshine and showers but highs of only 6C (43F) in Lerwick. Indeed, parts of London and Essex hit only 14C on Monday, making this the coldest Early May Bank Holiday on record, although records only date to 1978.
It took the Bank Holiday storm until Wednesday morning to clear off into the North Sea, so the Tuesday was a day of scattered wintry showers with temperatures below average at 7-13C (45-55F) - the seasonal average for early May 14-17C (63F). We even saw some lying snow down to about 150m in northern Scotland for most of the week.
The second weekend started very wet and windy as an area of low pressure crossed west to east, bringing heavy rain and 50mph winds on the Saturday, although temperatures were closer to the seasonal average in the south at 16C (61). Sunday was broadly dry and cloudy, with hazy sunshine and a few scattered showers mostly in Wales and the north. Sunday was much milder, dropping to only 12C (54F) on Saturday night and with highs of 21C (70F) in Essex, although it remained windy.
Week two of May began with a low pressure system over our western flank, resulting in scattered showers moving north and east through the day on Monday and repeated on Tuesday, accompanied by strong winds gusting to 40 mph. Wednesday was mostly dry and bright, with the occasional heavy shower UK-wide, but Thursday saw more persistent rain in the midlands and south west; mostly dry in the north and east. Parts of Wales saw a month's worth of rain, and by the 13th England had seen 92% of the rainfall we’d expect in an average May. Thursday's low pressure sank southwards into the Channel Islands overnight and Friday was a largely dry but cloudy day. Another large low arrived just in time for the weekend.
The middle weekend brought yet more wet weather, mostly in the south; the north missing the worst but remaining largely cloudy. Sunday saw persistent rain across most of England, prompting the Environment Agency to issue two red and seven amber flood alerts, particularly around Dorset and Somerset. Overall, temperatures were disappointing in low to mid- teens Celsius. This sunshine and showers theme continued through the third week, with southern areas receiving the bulk of the rain and, at times, gusty winds. Thursday and Friday saw an unseasonably deep area of low pressure moving across Ireland and bringing some heavy rain and gales to most of the UK - winds in excess of 60mph battered the south coast, south-west and Irish Sea, which is unusual for this stage in May. Indeed, The Needles on the Isle of Wight recorded a peak gust of 89 mph on Friday, while Capel Curig in Wales saw 103mm (4 in.) of rain in 24 hours. Temperatures during the week ranged from about 8C (46F) in Lerwick to 14C in the south east, the Mercury inching a little higher in the sunshine. Overall, the latter half of May seemed much more like October than late spring.
The penultimate weekend was a mixed affair. Once Friday's storm had pushed off towards the Nordics, the UK was left with sunshine and heavy showers, but with a gusty northerly airflow. On the Sunday another low swept across, bringing more wet and windy weather during the afternoon, albeit slightly lighter winds than we saw on Friday, lasting into the early part of the final week. May ended on a more summery note as high pressure built in and temperatures climbed back to the seasonal average of about 18C (64F) in the south east.
If you're interested in the wildlife to be found this month, including fledgling and cuckoos, glowworms and orchids, check out my Wildlife Watching - June article. More than any other month, June is the season of baby deer and, going by my social media feeds, there are some roe kids and sika calves around since the latter part of last month. Please remember that it is perfectly normal behaviour for mothers to leaves their kids/calves/fawns lying up on their own while they go off to feed. The dams will return every few hours to wash and suckle the youngster. In the vast majority of cases the deer has not been abandoned (this is very rare); please do not pick it up unless it’s in imminent danger.
Website news
Well, after about 18 months, the water deer research is finally sufficiently comprehensive (I can’t say “complete” because it’s anything but) for me to start work on the article and this is now underway. Unlike previous articles, my intention is to upload sections as I complete them, which should result in the content being available sooner, rather than spending two years writing it and sending my proof-readers into a depressive spiral when it hits their inbox.
In addition to starting work on the water deer piece, I am also working on a Speed Read on the common frog and, last month, a new QA went live touching on how deer manage to bark for such long periods without losing their voice. This QA is a minor expansion of a letter I wrote to the British Deer Society's Deer journal last year in answer to the same question.
In the news
A few news stories that caught my attention this month (not necessarily all recent) include covid detection dogs, a major project to restore coral reefs, and a warning about the rise in the demand for sand:
- Covid canines. A new study suggests that dogs can be trained to detect people infected with the Covid19 virus with staggering efficiency. An international task force of researchers coordinated by the WHO found that dogs were able to detect infections with up to 99% sensitivity and 98% specificity. Currently, lateral flow tests seem to correctly detect infections in 72% of people with symptoms and 58% of those without. The University of Pennsylvania School of Veterinary Medicine Working Dog Center is currently investigating whether dogs can differentiate between people with Covid-19 and those vaccinated against it.
- Reef restoration. Some 40,000 sq-m (10 acres) of coral reef has been restored as part of a huge conservation effort in the waters off Indonesia. The project uses steel frames that interlock to provide a foundation on which the coral can grow. One reef saw coral cover increase from 5% to 55%. The plan is to restore 185,000 sq-m (46 acres) by 2029.
- Marine masks. Environmental groups are calling for action after divers found surgical face masks littering a coral reef in the Philippines. Just 10 minutes into their first dive after lockdown, locals at Anilao counted 10-12 face masks.
- Keep calm. New research by scientists in Pennsylvania has found that honeybees sometimes overreact to parasites, putting the colony under unnecessary stress. The researchers found honeybees produced a warning pheromone when infected by the fungus Nosema ceranae and this caused a significant change in their behaviour that had the potential to disrupt the social status of the hive.
- Sand sirens. The boom in illegal mining of sand poses a risk to the world’s vulnerable river and lake systems. The recent demand for sand for building projects during lockdown and in response to military conflicts has resulted in unprecedented pressure on resources. Intense sand extraction in several of China's freshwater lakes has lowered water levels, increased the risk of droughts and endangered local wildlife.
Discoveries of the Month
Pongo pandit?
Growing up is a complicated business. Learning to become a member of society can be a challenge and we take our cues from our environment and the people around us. Humans aren't the only animals that engage in this "social learning", and it is particularly evident when we look at how animals learn what's good to eat and how to tackle particularly challenging food items that take skill to either acquire or break into.
Broadly speaking, ethologists (scientists that study animal behaviour) recognise three phases of social learning: animals initially learn from their main caregiver (typically their mother) and then expand to watching other members of the social group, copying their actions, before finally observing local individuals tackling novel situations once they've dispersed. Primates seem to adhere particularly well to the first two phases of this model, but outside of the human species we have little more than anecdotal evidence for phase three. Data from a new study of wild Sumatran and Bornean orangutans in Indonesia points to these great apes not only engaging in phase three learning, but also varying who they take their cues from based on their sex.
From 2007 until 2020, a team of researchers led by Caroline Schuppli at the University of Zürich studied interactions by wild Sumatran orangutans (Pongo abelii) at Suaq Balimbing in South Ace, while data on Bornean orangutans (Pongo pygmaeus) at Tuanan in Central Kalimantan were collected between 2003 and 2018. Sixty-four experienced observers followed the animals through the rainforest, recording their behaviour at two-minute intervals. When the animal being followed was seen to stop and watch the activity of another for at least five seconds from a distance of no more than five metres (16 ft.) it was considered to be "peering" - i.e. close range observation of what someone else is doing, followed by trying it out yourself.
Overall, the observations revealed that males and females didn’t differ significantly in their peering rates, but the data do show an interesting difference in the development of social interest between the sexes. Young females directed much more of their attention to their mothers than did immature males. Indeed, the juvenile males were more interested in the activities of immigrant individuals, particularly other males. Consequently, when looking at the diet of the youngsters at independence, females had a significantly greater overlap with their mother than the males did. Writing in the journal PLoS One last month, Schuppli and her colleagues suggest that orangs choose to learn from those with the most relevant ecological experience, speculating that:
"... these biases may be the result of increased social interest in feeding behavior of same sexed adult conspecifics and of individuals with corresponding dispersal ecologies."
In other words, looking at numerous different immigrant adults might help newly independent males to cope with the challenges of dispersal.
Source: Ehmann, B. et al. (2021). Immature wild orangutans acquire relevant ecological knowledge through sex-specific attentional biases during social learning. PLoS Biol. 19(5): e3001173. doi: 10.1371/journal.pbio.3001173.
Accelerated apodids
For me, the screech of swifts in a clear blue sky is a sign of summer. Despite sharing the same basic body plan, swifts aren't related to those other bastions of summer, the swallows and martins. Instead, they're members of their own family, the Apodidae, the name of which is a nod to the bird's predominantly aerial lifestyle that has led to the evolution of their weak legs; derived from the Greek ápous, meaning "footless". Indeed, swifts may spend up to 10 months every year on the wing, landing only to nest and raise their chicks and scientists at Edinburgh University recently found that their wing shape promotes the formation of leading-edge vortices that help dampen turbulence, allowing them to fly smoothly in even rough weather.
As well as being nimble in the air, swifts have a reputation for being, well, swift, as they hawk their fast-flying insect prey. We also thought they were pretty fast fliers on migration, too, covering up to 500km (310 miles) in a day, but recent estimates from a team of researchers in Sweden suggests this may have been a very conservative estimate.
In 2010, 2012 and 2014, Susanne Åkesson and Giuseppe Bianco at Lund University captured a total of 45 adult swifts in Swedish Lapland and fitted them with tiny geolocators, allowing them to track their migration. On average, the birds left their breeding grounds in Lapland in mid-August and arrived in the Sahara around the end of September to spend the winter, having stopped over mostly on the Iberian Peninsula for a day or two. The return migration was also recorded and found to be significantly quicker; the birds leaving Africa during mid-May and arriving back in their breeding grounds at the end of May or beginning of June.
The researchers calculated that the birds travelled, on average, some 570km (354 miles) per day, with the record during the study being 830km (516 miles) per day for nine days. The birds' airspeed wasn't, however, exceptional, hitting only about 10 metres per second (22 mph), but Åkesson and Bianco think that a combination of a tailwind in spring, which gives them an extra 20% boost, and their strategy of fly-and-forage, whereby they take airborne insect prey along the way rather than having to fuel up first, contribute to the remarkably rapid migration.
More interesting still was that the birds seemed able to accurately time their spring migration to make the most of the tail winds, choosing to leave on the day the winds offered the best boost. The scientists don't yet know how the birds predict this, although they suspect the birds may respond to changes in air pressure associated with passing weather systems.
Source: Åkesson, S. & Bianco, G. (2021). Wind-assisted sprint migration in northern swifts. iScience. 2021: 102474. doi: 10.1016/j.isci.2021.102474