Hampshire and Isle of Wight Butterfly and Moth Society
Hampshire and Isle of Wight Butterfly and Moth Society
| Family: | Nymphalidae |
| Subfamily: | Nymphalinae |
| Genus: | Vanessa |
| Species: | cardui |
| Authority: | (Linnaeus, 1758) |
This species is a migrant to our shores and, in some years, the migration can be spectacular. The most-recent spectacle, in 2009, is considered to be one of the greatest migrations ever, with sightings from all over the British Isles that are definitely on a par with previous cardui years.
This species originates from north Africa, and it has been suggested that the urge to migrate is triggered when an individual encounters a certain density of its own kind within a given area. This theory makes perfect sense, since this species can occur in high densities that result in foodplants being stripped bare on occasion with many larvae perishing as a result.
Unfortunately, this species is unable to survive our winter in any stage. This is a real shame, for not only does this species often arrive in large numbers, but is a welcome sight as it nectars in gardens throughout the British Isles in late summer. This butterfly has a strong flight and can be found anywhere in the British Isles, including Orkney and Shetland. An interesting fact is that this butterfly is the only butterfly species ever to have been recorded from Iceland.
| #Individuals | #Tetrads | 2022 | 2023 | Abundance Trend | 2022 | 2023 | Distribution Trend |
|---|---|---|---|---|---|
| 1563 | 2002 | +28% | 436 | 482 | +10% |
| #Records | #Individuals | Earliest Record | Latest Record | |
|---|---|---|---|---|
| All Records | 25,939 | 92,641 | 01/01/2013 | 31/12/1987 |
| 2023 | 1,343 | 2,002 | 9/4/2023 | 7/11/2023 |
| Location | Date | Quantity | |
|---|---|---|---|
| Earliest Record | Wildern Local Nature Reserve | 9/4/2023 | 1 |
| Latest Record | Godshill | 7/11/2023 | 1 |
| Highest Count | Horringford | 6/8/2023 | 19 |
One of the issues with 'raw' trend data is that there is inherent bias based on the number of recorders. For example, the number of individuals and populated tetrads recorded are likely to increase if there is an increase in the number of recorders. In order to remove this bias, the normalised trends use data that has been recalculated using the average number of recorders over the trend period. This normalisation gives a much better picture of the true trends.
Average #Recorders: 303.48
Average #Recorders: 303.48