COMMENTARY-Ipecac: an improved emetic for wild birds

Since Prys-Jones et al. (1974) and Tomback (1975) drew attention to the potential value of tartar emetic (antimony potassium tartrate) as a nondestructive method of obtaining food samples from wild birds, tartar emetic has apparently become widely accepted for this purpose (Carlisle and Holberton 2006, and references therein). Prys-Jones et al. (1974) did caution against its routine use, chiefly because of its toxicity, and the various studies cited by Carlisle and Holberton (2006) (to which we would add Herrera 1976 and Davies 1976) have reported mortality and other harmful effects. We suggest reasons for some of these problems and recommend an alternative. The chief drawbacks to tartar emetic are its toxicity if absorbed into the bloodstream and the difficulty of determining the correct dose (see Discussion). The toxicity of tartar emetic led to its abandonment some time ago for inducing vomiting in children who have swallowed poison (Goodman et al. 1996). An alternative that is rarely toxic and so is widely used for this purpose is ipecacuanha (usually abbreviated to ipecac), a natural extract from the roots of the rubiaceous plants (Cephaelis ipecacuanha or C. acuminata; Todd 1967). The use of ipecac for avian diet sampling was suggested by Kadochnikov (1967) and subsequently tested by Radke and Frydendall (1974) with poor results and using doses much smaller than we have found to be effective. Here we report on results from three separate diet studies where ipecac and tartar emetic were used to obtain samples from landbirds. In May 1977, one of us (V.C.F.) began using ipecac to obtain food samples from forest birds mist-netted in the Nguruman Hills, southern Kenya (2°S, 36°E). A.W.D. had been using tartar emetic in a parallel study in Kakamega Forest, western Kenya (0°30′S, 35°E), but after comparing results of the two chemicals, switched to ipecac. P.S.M. also used ipecac on wood-warblers (Parulinae) in northern New Brunswick, Canada (47°30′N, 67°30′W), in June and July 1998 and 1999. None of these studies were designed as a test of emetics; A.W.D. (unpubl. data) and V.C.F. (unpubl. data) both carried out intensive passive mist-netting (A.W.D. to study seasonality in a rainforest bird community, and V.C.F. as part of a survey of the birds of a little-known part of Kenya), and P.S.M. used targeted mist-netting with tape playback to verify diets in support of his study of the feeding ecology of selected breeding songbirds (McKinley 2003). Birds captured in Kenya were predominantly resident passerines of lowland forest and forest edge (A.W.D.) or of upland mixed forest (V.C.F.), whereas those in Canada were summer-resident passerines breeding in mature tolerant hardwood forest. In all three studies, the focus was on obtaining diet samples, not comparing emetics. However, the continuing use of tartar emetic in such studies (Carlisle and Holberton 2006, and references therein), and evident lack of awareness in the ornithological community of a safer alternative, prompted preparation of this analysis. Birds caught in mist-nets were placed in cloth bags and identified, banded, weighed, and measured, (A.W.D. and V.C.F.) or identified (P.S.M.) before the emetic was administered. Birds were selected for treatment based on several criteria, chiefly the need for diet information (targeting taxa of mixed or unknown diet) and the capture rate (birds were treated only when time allowed). Ipecac and tartar emetic were both administered through a hollow plastic tube inserted down the esophagus (Poulin et al. 1994). Tartar emetic doses were 0.025 ml/g body weight of a 1% solution in water, based on those recommended for medical use. Ipecac can be obtained either as a tincture (the formulation used in Kenya) that can be diluted with water, or as a syrup that can be dripped into the back of a bird's throat with a pipette and the bird will often drink freely as soon as it detects the sweet taste. Doses were based on rates recommended (on the packaging) for children; A.W.D. and V.C.F. used 0.1 ml per g body mass of a 1:20 solution by volume of the tincture in water, administered in the first of the two methods outlined above. P.S.M. used a dose of 0.1 ml per g body mass of the syrup (that contained 7% powdered ipecac). Immediately after the emetic was administered, birds were placed in either a plastic or aluminum container with either a flexible press-down lid or a plastic cover with a fist-sized hinged door. The container was large enough to present no risk of suffocation to a small bird kept there for a few minutes. A dark cloth was placed over the container to quiet birds that normally regurgitated within 2 min. Birds were checked frequently because they sometimes regurgitated immediately. On one occasion, a bird ate the food it had just regurgitated, indicating that ipecac did not cause aversion to food as tartar emetic may do (Zach and Falls 1976). Regurgitate was removed with a combination of forceps and small paintbrush, or a strip of paper, after the bird was released. We attempted forced regurgitation using tartar emetic on 63 individuals of 29 species representing 9 families of birds in Kakamega (A.W.D.) and using ipecac on 95 individuals representing 17 families in Nguruman (V.C.F.; Table 1). The effectiveness in inducing vomiting did not differ significantly between the two samples (χ21= 1.8, P > 0.1). Prys-Jones et al. (1974) found tartar emetic to be more effective for insectivores than granivores, but, in our study, too few granivores were treated with tartar emetic to compare effectiveness by food type. The recapture rate did not differ significantly between untreated birds and those treated with tartar emetic (χ21= 1.96, P > 0.1), but the recapture rate of birds treated with ipecac was significantly higher than that of untreated birds (χ21= 9.3, P < 0.001). Birds treated with ipecac were not more likely to be recaptured than those treated with tartar emetic (χ21= 3.2, P= 0.07). Three birds died within a few minutes of receiving tartar emetic, but there were no casualties with ipecac. All 44 warblers treated with ipecac in northern New Brunswick regurgitated, including 24 Black-throated Blue Warblers (Dendroica caerulescens), 18 Black-throated Green Warblers (D. virens), and two American Redstarts (Setophaga ruticilla). Most did so within 30 s of treatment, producing identifiable arthropod remains (McKinley 2003). Several of the treated birds perched nearby and started singing and foraging immediately after being released. One Black-throated Green Warbler treated in 1998 was recaptured 2 wk later, and two Black-throated Blue Warblers treated in 1999 were recaptured 2 wk later. Although we recommend the use of ipecac rather than tartar emetic because it is less toxic, it is constructive first to review the drawbacks that have been found with tartar emetic and suggest some possible reasons for some of them. Herrera (1976) suggested that too small a dose of tartar emetic could be more harmful than an overdose, presumably because it failed to induce vomiting and allowed the emetic to be absorbed into the bloodstream. In experimental studies using tartar emetic with captive Ovenbirds (Seiurus aurocapillus), Zach and Falls (1976) reported high mortality rates (12.5–50%). However, they used a dose of 0.3 ml of a 1% solution on birds weighing about 18–20 g, or about half the dose that A.W.D. used on wild birds of similar mass in Africa. We suggest that Zach and Falls (1976) used too low a dose, and this might also explain the 8.5% mortality reported by Herrera (1976), although he did not state the dose he used. Poulin et al. (1994) used 0.8 ml per 100 g body mass of a 1.5% solution on over 3000 birds in Venezuela, incurring 2% mortality in both treated and untreated birds. Zduniak (2005) administered glucose to Hooded Crow (Corvus corone cornix) chicks immediately after they regurgitated in response to tartar emetic, and attributed the lack of mortality or other side effects to the glucose. A further contributor to mortality may be stress. Zach and Falls (1976) found 50% mortality in Ovenbirds “exposed to the additional stress associated with capture” and cautioned against the use of tartar emetic. When stress is reduced to a minimum, by processing the birds at or very close to the site of capture and releasing them immediately as we routinely did, harmful effects can be reduced. Stress probably contributed to the 17.5% mortality of Pied Wagtails (Motacilla alba) treated with tartar emetic by Davies (1976); all the birds that died were in a large group captured together at a roost and subjected to considerable stress and delay in being processed, but no birds caught singly or in groups died (N. B. Davies, pers. comm.). We have suggested reasons why tartar emetic may be less harmful than some studies indicate, but its known toxicity remains a disadvantage. Carlisle and Holberton (2006) suggested its use should be abandoned in favor of fecal samples, and we agree that a sufficient case has now been made to abandon the use of tartar emetic on birds. However, because fecal samples do suffer from the disadvantage that soft parts of prey are under-represented (but see Ralph et al. 1985), we suggest that investigators consider ipecac as a safe alternative. One of ipecac's chief advantages is that its effectiveness depends less on the amount of emetic administered (which is crucial in the case of tartar) than on the amount of fluid administered with it (Todd 1967). Therefore, dosages of ipecac are much less likely to reach a toxic level. As in tartar emetic studies (e.g., Poulin et al. 1994), we found it important to get the syringe tube all the way down into the stomach and this could be determined by the length of tubing inserted. Failure of the tube to reach the stomach delayed regurgitation or prevented it altogether. We found that birds treated with ipecac were more likely to be recaptured than those not treated. Differences in species composition between the treated and untreated samples may have contributed to this result; we targeted species whose diet was poorly known, so treated birds were not a random sample of the species caught. For example, birds in the family Pycnonotidae (bulbuls) contributed 26% of the treated sample, but only 13% of the total sample, and had a disproportionately high recapture rate of 37% (V. C. F., unpubl. data). Compared with tartar emetic, syrup of ipecac is at least as effective, is freely available from pharmacies in both Canada and the United States, and is less toxic. Ipecac remains the emetic of choice for children who have ingested poison. The syrup formulation is preferable to the tincture that is more concentrated (Goodman et al. 1996), less widely available, and contains some alcohol. It would be useful to compare the relative effectiveness of syrup of ipecac and fecal sampling in studies of the diet of wild birds in terms of recapture rates, energetic condition, and usefulness in assessing diet. Examination of posttreatment activity in a laboratory setting would also be useful for assessing possible interference with foraging. Pending such research, we recommend that investigators using an emetic to study bird diets use ipecac rather than tartar emetic. We thank C. Fayad and the late E. Diamond for help in the field and in compiling data, R. Prys-Jones for encouragement in pursuing the topic, and J. Carlisle and two anonymous reviewers for improving the manuscript. This is ACWERN Publication No. UNB-62.

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