Thistles have been said to be very important nectar sources for pollinators. Some ecological organizations, such as the Xerces Society, have attempted to raise awareness of their benefits, to counteract the general agricultural and home garden labeling of thistles as unwanted weeds. The monarch butterfly, Danaus plexippus for instance, was highlighted as traditionally relying upon taller large-flowered thistle species such as Tall thistle, Cirsium altissimum, for its migration. Although such organizations focus on the benefits of native thistles, certain non-native thistles, such as Cirsium vulgare in North America, may provide similar benefits to wildlife. Some prairie and wildflower seed production companies supply bulk seed for native North American thistle species, for wildlife habitat restoration, although availability tends to be low. Thistles are particularly valued by bumblebees for their high nectar production. Cirsium vulgare ranked in the top 10 for nectar production in a UK plants survey conducted by the AgriLand project which is supported by the UK Insect Pollinators Initiative. Bull thistle was also a top producer of nectar sugar in another study in Britain, ranked third with a production per floral unit of (2323 ± 418μg).