Are camouflaged seeds less attacked by wild birds?

Abstract

Wheat, corn and rice crops in Brazil use seeds treated with systemic insecticide/nematicide carbofuran, mixed to rhodamine B red dye. Carbofuran is toxic and rhodamine B is attractive to wild birds that eat up these seeds, resulting in notable mortality during planting. A field experiment was performed in southeast Brazil to evaluate if camouflaged seeds would be less consumed by wild birds in comparison to commercial seeds with red-colored rhodamine B and aposematic blue seeds. Camouflaged seeds were less removed than seeds with rhodamine B and natural colors. The camouflaging was more effective in the presence of irregularities and litter. There was no removal of blue-colored seeds. As legislation requires treated seeds to receive a different color to avoid accidents with humans, camouflaging may be used as replacement of rhodamine B to reduce mortality rates of wild birds. Key words: seed camouflage, carbofuran, rhodamine B, visual repellents, bird mortality Sementes camufladas são menos atacadas por aves silvestres?RESUMO: Plantações de trigo milho e arroz no Brasil utilizam sementes tratadas com o inseticida e nematicida sistêmico carbofuran, associado ao corante vermelho rodamina B. O carbofuran é tóxico e a rodamina B é atrativa às aves silvestres, as quais consomem estas sementes, resultando em notável mortalidade durante o plantio. Um experimento realizado em campo agrícola no sudeste do Brasil mostrou que sementes camufladas foram menos removidas por aves silvestres do que sementes com rodamina B. A camuflagem foi potencializada em presença de irregularidades e serrapilheira no solo. Não houve remoção de sementes de cor azul, mas a formulação granular de cor azul tem causado mortalidade de aves nos USA e Canadá. Como sementes tratadas com agrotóxicos devem, de acordo com a legislação, receber coloração diferenciada para evitar acidentes com humanos, a camuflagem pode ser utilizada, substituindo a rodamina B. Palavras-chave: camuflagem de sementes, carbofuran, rodamina B, repelentes visuais, mortalidade de aves

Camouflage of Seeds, a Control Method of the Bird Mortality in Grain Crops

“…In despite of non significative at 5%, the highest removal of seeds camouflaged with industrial liquid dye in the treatment 5, shows the importance of superficial grooving in the coverage, attributed to the powder dye in the least removed camouflaged seeds in Trials 1 and 2 (Almeida et al, 2010b). These results suggest that the efficiency of the camouflaging is not only characterized by the brown dye, or because of the similarity of shades between the soil and the seeds, but also by a group of factors attributed to the seed coverage and the background, like opacity and superficial grooving in the seed, and the presence of irregularities and organic matters on the soil surface.…”

“…Thus the toxicity of carbofuran would overrun any of the potentially beneficial effects of methiocarb. Finally, a third field study, performed in two trials (Almeida et al, 2010b) aimed at evaluating if camouflaged seeds would be less consumed by wild birds in comparison to commercial seeds coated with red-colored rhodamine B and blue seeds (Avery et al, 1999;Hartley et al, 1999;2000). Seed removal experiments were performed in an area reserved for annual planting of 2.78 ha in southeast of Brazil, where, because of the frequent planting of corn and other cultures, a great deal of granivorous birds could be found at the site.…”

“…Nonetheless, there were no differences on removal rates among camouflaged seeds. Apparently it may not be necessary having major similarities of shades between camouflaged seeds and the soil to prevent higher consumption rates (Almeida et al, 2010b). Such observation is supported by Merilaita & Lind (2005), who concluded that the exact similarity of color among the prey and the background is neither enough, nor necessary to minimize the probability of detection by the predator.…”

“…Improved camouflage prototypes, whose ingredients were evaluated in Section 3.1.2.2, were tested for germination (section 3.2.3), regarding the seeds removal by birds in agricultural field (described in section 2, Almeida et al 2010b) and then using this same experiment, the performance of these prototypes will be discussed, regarding the response of the camouflaged covers to weather during five days of exposure, usually when the seeds germinate until the third day after sowing. The lowest numbers of removals were found for seeds which camouflage was based on powder dye, water, liquid dye, and acrylic glue (Table 5, treatments 3, 4, 5).…”

“…This can be inferred, considering that, despite the lack of consumption of blue color seeds in some experiments (Hartley et al, 1999, 2000, Almeida et al 2010b) the use of carbofuran in the granular formulation of the same color has been banned in Virginia, USA and Canada, due to bird mortality caused by direct ingestion of the product (Almeida et al, 2010b). Moreover, there has been no communication observed between poisoned birds and healthy ones, that could stop the consumption, even when expressive mortality rates occur and in the presence of obvious agonistic behaviors caused by the ingestion of seeds treated with carbofuran, methiocarb carbosulfan or in combination with conspicuous colors such as beige and red (Almeida et al, 2010a;Almeida & Almeida, in press).…”