Academic journal article The American Midland Naturalist

Use of Fine-Textured, Mineral-Rich Soils by a Northern Flicker (Colaptes Auratus) in North-Central British Columbia

Academic journal article The American Midland Naturalist

Use of Fine-Textured, Mineral-Rich Soils by a Northern Flicker (Colaptes Auratus) in North-Central British Columbia

Article excerpt


Consumption of soils (geophagy) by animals occurs in several classes of vertebrates and is well-known and widespread (Brightsmith, 2004). Why animals consume soil is debatable (Diamond et al., 1999) but is likely related to a need to boost mineral uptake, increase buffering of the intestinal pH, or as a way to detoxify plant toxins (Jones and Hanson, 1985; Gilardi et al, 1999). Theories about why birds specifically consume soils range from use of large particles (grit) for grinding ingesta (Diamond, 1999), to the consumption of fine-textured soils with elevated mineral content for mineral supplementation and/or elevated cation exchange capacities for use in detoxifying plant metabolites (Brightsmith el al., 2008).

Elevated sodium concentrations have been linked to the use of soils by Peruvian Parrots and Macaws (Brightsmith et al, 2008; Powell et al., 2009), while high levels of calcium and iron have been found in soils used by Maroon-fronted Parrots (Rhynchopsitta tenisi) and Cassowaries (Casuarius bennetti) (Symes et al., 2006; Valdés-Peña et al, 2008). Magnesium and other important dietary elements are also found in soils and may or may not be related to a drive in birds to consume soils (Gilardi et al, 1999; Powell et al, 2009).

Parrots, pigeons, and doves in several countries of South and Central America are known to obtain fine-textured clays from mineral licks (Brightsmith et al, 2008; Valdés-Peña el al., 2008). Parrots, pigeons, hornbills, and crows in New Guinea have also been documented eating nongrit soils (Diamond et al, 1999) as have hand-reared geese in Bavaria (Wink et al., 1993). Reports of North American birds consuming natural, fine-textured, mineral-rich soils, however, are rare (Emmons and Stark, 1979).

Here, 1 describe the consumption of clay soils from an expansive clay bank in north-central British Columbia, Canada by a Northern Flicker (Colaptes auratus L.) and speculate as to why the bird may have been ingesting these soils. Given the use of soils by tropical birds for the purposes of mineral supplementation and detoxification of plant metabolites, I hypothesized the consumption of clay soils by the Flicker was for a similar purpose. I tested my hypothesis by collecting and analyzing, for texture and mineral composition, the soils used by the Flicker and then compared these values to those reported by others documenting geophagy in birds.



Observations were made approximately 50 km southwest of Prince George, British Columbia, Canada on the west side of the Chilako River (53°27'13.3'N, - 123°12'21.0"W) on 26 September 2015. The habitat surrounding the clay bank is riverine and bordered by agricultural lands and a patchwork of mixed deciduous-coniferous forests. Here, the dominant conifer species and trees in which Northern Flickers are known to forage (Edworthy el al, 2011) are I.odgepole Pine (Irinus contarla var. lasiocarpa), most of which are now dead due to a recent Mountain Pine Beetle (Dendoctronus ponderosae) outbreak, and Douglas Fir (Pseudotsuga menziesii var. glauca) with some hybrid White Spruce (Picea mgelmannii X glauca) and Subalpine Fir (Abies lasiocarpa) in cooler wetter sites. The deciduous component of the surrounding forest is comprised mostly of Trembling Aspen (Populus Iremuloides) with some Paper Birch (Betula papyrifera) and scattered large Cottonwoods (Populus balsamifera ssp. trichocarpa), many of which are used by Flickers for nesting (Aitken et al, 2002). The weather at the time of the observation, which occurred just after 2 pm, consisted of clear skies and a temperature of approximately 15 C.


To determine characteristics of the soil used by the Flicker, two samples of soil were collected from the clay bank where the observation was made at the point where the Flicker was excavating. Soils were dried to a constant weight at room temperature for 15 d at the Enhanced Forestry Laboratory at the University of Northern British Columbia. …

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