Volatile weather led to an influx of exciting migrant species in 2019 but is putting pressure on some homegrown flora and fauna, according to an annual audit of the UK’s environment.

Many unusual birds and butterflies ended up on UK soil over the past 12 months, whisked in by high winds or attracted by unseasonably hot spells, and there was good news for native grey seals, dragonflies and wildflowers, the survey from the National Trust reveals.

But the erratic conditions made it a challenging year for a string of other resident species, including water voles, terns, toads and puffins.

Ben McCarthy, the head of nature conservation and restoration ecology at the National Trust, warned that the changing weather patterns could lead to some species becoming extinct unless action is taken.

He said: “Sightings of migrant insects and birds are becoming more common. This is a result of our changing climate. Although this can seem exciting, the obvious flipside is how these changes will start to affect some of our native species already under pressure from intensive land use, habitat fragmentation and climate change.

“More mobile species might be able to escape unfavourable conditions, but they’d have to find similar conditions elsewhere. The biggest threat is to less mobile species and those that are specialists.”

Warm weather in the early months of 2019 led to an influx of migrant butterflies, moths and dragonflies from the south and east. For example, significant numbers of painted lady (Vanessa cardui) butterflies were seen arriving en masse for the first time in a decade.

Numbers of the Clifden nonpareil moth, which has a rare blue underwing, were at their highest for at least 25 years, while in June, July and October there were good numbers of spectacular migrant dragonflies, including the red-veined darter and vagrant emperor.

Grey seals around the UK shores also appear to be thriving, with numbers up this year despite the high 50% mortality rate of seal pups.

Certain wildflowers, especially orchids, did well, possibly due to last year’s drought. There were record numbers of bee orchids, dark-red helleborine and autumn lady’s tresses at some sites.

However, the picture was grim for other species.

The fires on Marsden Moor in West Yorkshire damaged 700 acres of precious habitat for mountain hares and ground-nesting birds such as curlew and twite, undoing years of peat restoration work.

Facebook Twitter Pinterest A fire on the Close Moss, part of Marsden Moor, in February. Photograph: Jon Super/Reuters

It was another challenging year for natterjack toads, who rely on pools of water in their dune habitat to thrive. Because many of these dried out in May and June, spawn and tadpoles were lost.

Heavy periods of rainfall affected many species this year, according to the audit. Water voles at Malham Tarn in the Yorkshire Dales suffered due to heavy and unexpected rainfall in June, July and September. Sudden flooding can result in the loss of young, who are unable to swim.

Arctic terns, puffins, guillemots and shags all suffered losses due to significant rainfall on the Farne Islands, Northumberland, in June.

McCarthy said the audit brought home the importance of making sure current habitats are protected and new ones created. He added: “If our wildlife doesn’t have anywhere to move to as temperatures rise and the weather changes, over the coming years we will inevitably see more and more species at risk of becoming extinct.”

Keith Jones, a climate change expert at the National Trust said: “This year’s changeable weather is a symptom of the warming climate. The more our temperatures go up – the more erratic our weather will become. This will force changes to the life cycles of many species as food webs are knocked out of sync.”

These were some of the survey’s findings:

January to March

The year began generally fairly settled over most of UK but this was followed by a blast of snow. There were significant sightings of yellow-browed and Pallas’s warblers, probably driven in by cold weather from continental Europe. The hottest winter day on record was experienced in London on 21 February: 21C. This led to exceptionally early migrant birds, including swallows, house martins and sand martins. Rarities included a red-rumped swallow at the Cwm Ivy salt-marsh in Swansea. There was an early pulse of flowering dandelions. In late March the banded demoiselle damselfly, which typically emerges in mid-May, was seen in south London.

April to June

In April, Storm Hannah shredded fragile new leaves on trees, probably also impacting nesting birds. It was cold early in May with snow on hills in North Wales and northern England. Cranes bred at Wicken Fen in Cambridgeshire for the first time in at least 120 years. Swifts arrived late – well into May instead of late April. In June, bee orchids flowered profusely. Some had more than 77 flowers on a single stem, in contrast to last year, when there were only about nine. This is most likely due to last year’s heatwave.

July to September

Migrant moths, including the small marbled, were abundant across the UK and there were good numbers of the western bee-fly in Cheddar Gorge in Somerset. A worrying die-off of adult Arctic terns for a while in Northumberland, caused by botulism in pools where birds bathe. High tides flushed the pools out and the problem stopped. The first confirmed sighting of a brown booby in the UK was claimed by birdwatchers in Cornwall. It was probably blown in from the Caribbean or Mexico. A rare oak polypore fungus – a bracket fungus – was discovered at Ickworth, Suffolk.

October to December

Red-eyed vireos, north American birds, were seen on Lundy island off the Devon coast and the Lizard, Cornwall. Man o’ war jellyfish were blown on to beaches in Cornwall. Grey seals increased in numbers at Strangford Lough, Northern Ireland, in contrast to the harbour seal (common seal), whose numbers appear to be dropping each year. Leaves stayed on trees longer than usual, particularly beech and oak. A pair of snow buntings was seen on Bradnor Hill in Herefordshire, the first in the county since 2006.