- Local distribution and rarer species
- National B and rarer
|Rhoose Point AM||Llandaff North GT||Gorseinon BS||Templeton Ave DS||Cwmbach ME||Sea View VS|
|Nationally Scarce A||1||2||1||1||1||2|
|Nationally Scarce B||2||4||10||6||2||8|
|% of local and rarer in total||16||16||22||17||19||26|
|% of National B and rarer in total||2||2||3||1||1||4|
Whilst this has not supported my initial thoughts on the proportion of less common species at my trap site, it's interesting to see the disparity in the results. Unsurprisingly the traps in rural sites do better (apart from mine!). I wonder if there is a sampling bias here though, all sites apart from mine have long records and I have a suspicion that in the early years all the common species are picked up quite quickly and dominate the record, which may mean that as the years go by it becomes proportionately more likely that new species encountered are in the Local distribution or rarer categories...?
I'm sure you're right that the longer you trap at a site the greater the % of uncommon species you'll record.ReplyDelete
It stands to reason that uncommon species will generally occur in smaller numbers than common species. Also, rarer species tend to be more sedentary so will probably wander less often from their habitats into your garden. Both of these factors mean they're less likely to turn up in the trap, but over a long time period you might get the odd one.
Another possible factor is that moths in general have become scarcer and are arriving at trap in smaller numbers. This probably affects scarce and local species as well as the common ones, so scarce and local species are getting numerically scarcer increasing the odds against them coming to a particular trap. Sites with a longer trapping history would have benefited from the comparative abundance of moths in the early days. There are species I used to get annually, a decade ago, that I now haven't seen for years.ReplyDelete