BBC Springwatch presenters revealed they are concerned species may be struggling with the "unusual spring".
The new series returned for its second episode on BBC Two on Wednesday, live from Wild Ken Hill in west Norfolk with presenters Chris Packham and Michaela Strachan.
The show is also hosted by Iolo Williams, presenting from Alladale in Scotland, and Gillian Burke from Strangford Lough in Northern Ireland.
During Wednesday's episode, Mr Packham and Ms Strachan spoke about the activity of birds they had been watching after cameras were set up around Ken Hill Estate, and viewers were treated to footage of three newly hatched kestrels being fed.
Mr Packham said it has been a very "unusual spring", particularly for species such as swallows, which he said a lot of people have noticed.
Ms Strachan said nature is allowed to thrive at the farm, which has been crowned a "fabulous mosaic of habitats", with mammals, waders, birds of prey and farmland birds making up 2,500 species on the site.
And Mr Packham said these species may be struggling with the weather, showing an example of buzzards sitting in a nest taking "a drenching".
Ms Strachan added: "It's confusing for the wildlife, it's confusing for us. We don't know whether to put our waterproofs on or our t-shirts."
He later added that they were concerned the heavy rain may be restricting the amount of insects prey birds like swallows can find.
He said: "What's led to those suspicions is that there are three young in the nest, typically a clutch of swallows would be four or five eggs."
Ms Strachan later spoke about the benefits of tree-hugging while holding on to a 180-year old tree, saying scientific evidence proves it good for mental wellbeing.
Springwatch has scaled down the numbers on-site for this year's show and dispensed with the studio, and presenters and technicians will use a fleet of electric buggies to take them around the estate.
Speaking to journalists on Monday, Mr Packham said he had struggled to find a charging point for his electric car.
He said: "There were no chargers in King's Lynn, none in Peterborough.
"So come on Norfolk, you need to get some charging points in."
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