The Lesser Slave Lake Bird Observatory is busy monitoring breeding birds, as well as insects and spiders with relatively new arthropod surveys started in 2021. Once per ten-day period during beat-sheet surveys, a square sheet is held under a branch which is hit exactly ten times to shake insects off which we identify and count. Photos of some of these bugs are uploaded to our iNaturalist account (@LSLBObs).
Songbirds may time hatching their eggs to match insect peaks. If peak insect timing shifts, younger birds could have less food or lower quality food and become less fit or even starve. The importance of healthy insect populations as a prerequisite for healthy bird populations cannot be overstated.
Most people are aware that males and females of many bird species look different, which is called sexual dimorphism. For example, the mottled browns of a female Mallard are remarkably different from the clean browns and green head of a male. But having males and females of the same species appear different is not unique to birds.
Sexual dimorphism can also be seen in some arthropod species found during our beat-sheet surveys. The easiest to see is in most spider species how females have big ‘butts’ (abdomens) and males have large club-like ends to the appendages near their mouths (pedipalps).
But some spider species take it further. A common species you may have seen if you admire flowers is the Goldenrod Crab Spider. Females of this species are large and bright yellow or white with genetically-determined red patterns, while males are much smaller and dark overall.
Female Goldenrod Crab Spider 
Male Goldenrod Crab Spider
Amazingly, female Goldenrod Crab Spiders can change colours based on the flower colours she sees around herself (Insausti et al. 2012). The base colour of a female is white, but she is able to secrete a yellow pigment from cells below her outer cell layer into her ‘skin’. Since she first needs to create the yellow pigments, it may take 10 to 25 days for her to change from white to yellow, but to change back to white takes only about six days (Insausti and Casas 2008). Eating colourful insects may also influence a female’s colour as her food’s colouring may show through her thin ‘skin’ (Schmalhofer 2000). Male Goldenrod Crab Spiders have not been documented undergoing these colour changes – perhaps because they travel larger distances in search of mates.
Bronze Jumping Spiders are another species that exhibit extreme sexual dimorphism; males have an overall blackish body and two light stripes down the sides of his abdomen, while females are larger and light brown with dots on her abdomen. Although, when exposed to insecticides, all Bronze Jumping Spiders have a harder time learning and navigating their environment, specific impacts differ between the sexes. Males have a harder time searching for prey, but females have a harder time catching prey (Royaute 2015).
Female Bronze Jumping Spider 
Male Bronze Jumping Spider
If you want to help our birds by helping our spiders and insects, plant native species in your landscaping whenever possible to provide a strong base to local food chains. Reducing pesticide use in the yard, garden, or farm can also help insects. Pesticides often kill much more than you are targeting and have sublethal effects higher up the food chain which may impair a birds ability to feed themselves, their young, or to even migrate (Moreau et al. 2022, Grace et al. 2024).
By Robyn Perkins, LSLBO Bander-in-Charge
References
Grace J, Duran E, Ottinger MA, Maness T. 2024. Sublethal effects of early-life exposure to common and emerging contaminants in birds. Current Research in Toxicology. Jul 31 (7): 100190.
Insausti TC, Casas J. 2008. The functional morphology of color changing in a spider: development of ommochrome pigment granules. Journal of Experimental Biology. 211 (5): 780–789.
Insausti TC, Defrize J, Lazzari CR, Casas J. 2012. Visual fields and eye morphology support color vision in a color-changing crab-spider. Arthropod Structure and Development. 41 (2): 155-163.
Moreau J, Rabdeau J, Badenhausser I, Giraudeau M, Sepp T, Crépin M, Gaffard A, Bretagnolle V, Monceau K. 2022. Pesticide impacts on avian species with special reference to farmland birds: a review. Environmental Monitoring and Assessment. 194: 790.
Royaute R, Buddle CM, Vincent C. 2015. Under the influence: sublethal exposure to an insecticide affects personality expression in a jumping spider. Functional Ecology. 29 (7): 962-970.
Schmalhofer VR. 2000. Diet-induced and morphological color changes in juvenile crab spiders. Journal of Arachnology. 28 (1): 56-60.
