For this week's feature on collective nouns, I'm doing something a bit different and taking a look at two species, not just one. Why? Because both species only have one recognised collective noun, which in both cases is unique to that species. Early spring also happens to be a good time of year to see both.

First up is the bullfinch. This dumpy finches can be difficult to see at any time of year, but it's worth looking for them at this time of year before the leaves emerge and start to obscure them again. With luck, you might find a male singing to establish his territory, though the song is hardly what could be described as tuneful, or loud. That's why I find it strange that a flock of bullfinches is known as a bellowing of bullfinches. I'd certainly never describe them as bellowing, but I guess that this is play on words. After all, bulls bellow, so why not bullfinches.

In the past it wasn't uncommon to see a bellowing of bullfinches. In fact, they were considered pests in many orchards as they have a liking for eating the buds from fruit trees. The loss of orchards and tall hedgerows may be factors in their recent declines. Luckily, we have several pairs here at Minsmere, where they are best seen around the car park entrance, in the North Bushes, or along the entrance road. They are shy birds, though, and you are most likely to spot one if you are the first visitor of the day, so it pays to get up early! 

Despite the male's vivid pink breast, they can be difficult to spot when perched, but once they fly you should see the bright white rump - a very useful ID feature shared with few other small woodland birds. As with many finches, the females are plainer, for better camouflage, though they share the white rump and black cap of the male.

A similarly sized woodland bird, the nuthatch, is much bolder, and louder. There were several nuthatches uttering their trilling call on my walk today, and we still have at least two of them regularly visiting the feeders at the visitor centre.

Nuthatches are distinctive birds, with bluish upperparts, buff bellies and a black bandit mask through the eye. They also have dagger-sharp bills with which they can easily crack open acorns and hazelnuts. It's thought that the name derives from the Turkish word "nuthak", meaning to crack nuts. 

As well as their unusual name, nuthatches have a unique behaviour, among British birds, in that they can climb headfirst down a tree trunk. They also have one of the weirdest collective nouns that I've encountered, and one for which I can find no obvious explanation. If anyone can shed any light on the origins of the term a booby of nuthatches, please let me know!