Sensitivity Analyses of a Population Projection Model of Ring-Necked Pheasants

Abstract A large literature exists on population dynamics of ring-necked pheasant (Phasianus colchicus) in North America, but there has not been an attempt to formulate a matrix model nor a sensitivity analysis of the relationships between vital rates and population finite growth rate (Λ) that can be used to guide management. We summarized demographic data available from a 5-year field study in Iowa, USA, collected in Kossuth County (low composition of perennial habitat) and Palo Alto County (high composition of perennial habitat) into a 2-stage (young and adult) matrix projection model. We estimated Λ₁ (the dominant eigenvalue of the deterministic matrix), the stable age distribution (ω), relative reproductive value vector (n̈), other demographic parameters, and Λ_iid, a bootstrap estimate of growth that includes interannual variation in life history parameters. We analyzed the relative importance of vital rates on population growth rate using sensitivity and elasticity of both matrix elements and lower-level parameters such as winter survival and nest success. We first characterized general life history using averaged data from both areas and all years that yielded Λ₁ = 1.086, and a stable stage distribution of. Minimum success of the initial nesting attempt (H₁) that would maintain Λ ≥ 1 under average conditions was estimated to be 42%. Changes in Λ₁ were most sensitive to survival of chicks during brood rearing (S_B), followed in importance by survival during the subsequent winter (S_W), followed by H₁. We followed the general analyses with analyses that helped us to focus on the differences in the landscapes of northwest Iowa. Λ_iid was ≥1 in only 9% of simulations of data from Kossuth whereas estimated Λ_iid was ≥1 in 88% of simulations from Palo Alto. Our analyses of the relative importance and interactions between S_B, S_W, and total recruitment (M, including H₁ and renesting), if combined with data more specific to a local area, would guide management aimed at affecting multiple life history stages whose relative importance will vary across the landscape.     

Giving‐up densities and ideal pre‐emptive patch use in a predatory benthic stream fish

1. We used observational and experimental field studies together with an individual‐based simulation model to demonstrate that behaviours of mottled sculpin (Cottus bairdi) were broadly consistent with the expectations of Giving‐Up Density theory and an Ideal Pre‐emptive Distribution habitat selection model. 2. Specifically we found that: (i) adult mottled sculpin established territories within patches characterised by significantly higher prey densities and prey renewal rates than patches occupied by juveniles or randomly selected patches; (ii) patches abandoned by adult sculpin possessed significantly lower prey densities than newly occupied patches, although this was not true for juveniles; (iii) the observed giving‐up density (GUD) for adult sculpin (i.e. average prey density in patches recently abandoned) increased linearly with increasing fish size up to the average prey density measured in randomly selected patches (i.e. 350 prey items per 0.1 m²) and decreased with increasing sculpin density and (iv) juveniles rapidly shifted their distribution towards the highest quality patches following removal of competitively dominant adult sculpin. 3. These results provide the first evidence of the applicability of GUD theory to a stream‐dwelling organism, and they elucidate the underlying factors influencing juvenile and adult sculpin habitat selection and movement behaviours. Furthermore, optimal patch use, ideal pre‐emptive habitat selection and juvenile ‘floating’ provide behavioural mechanisms linking environmental heterogeneity in the stream benthos to density‐dependent regulation of mottled sculpin populations in this system.     

Tetranucleotide microsatellites for aquila and haliaeetus eagles

A unique community of four syntopic eagle species exists in north‐central Kazakhstan. Questions about behaviour and genetics in these four species would benefit from the development of microsatellite markers. We isolated eight polymorphic microsatellite repeats (AAAG)_n from the eastern imperial eagle (Aquila heliaca) genome using a hybridization enrichment technique. These loci revealed moderate diversity in a local population of eastern imperial eagles (observed heterozygosity 0.26–0.78), and were also polymorphic in steppe eagles (A. nipalensis) and white‐tailed sea eagles (Haliaeetus albicilla). These primers may be polymorphic in other species of Aquila and Haliaeetus eagles.     

Discussion of Work on Isospora Species1

Comments are made concerning the work reported at this Conference by Dr. Edith Box. The importance of stress on the animals used in experimental work is emphasized. Difficulties in identification of isosporan species in birds are mentioned.     

Glycoalkaloid increase in Solarium tuberosum on exposure to light

Tubers of six commercially available potato cultivars were placed in bright light (140 jUmol“¹ m”²), approximately equivalent to dull daylight, for a continuous period of up to seven days. The tubers were sampled at intervals, scored for degree of greening, freeze-dried and subsequently assessed for glycoalkaloid and chlorophyll content. There were significant differences between the cultivars in their rates of greening and increase in glycoalkaloid content. There was an apparent relationship between the two characters. Increases in the individual glycoalkaloids a–chaconine and a-solanine were also assessed. The results are discussed in terms of the implications for the potato industry.     

Isotopic composition of transpiration and rates of change in leaf water isotopologue storage in response to environmental variables

During daylight hours, the isotope composition of leaf water generally approximates steady‐state leaf water isotope enrichment model predictions. However, until very recently there was little direct confirmation that isotopic steady‐state (ISS) transpiration in fact exists. Using isotope ratio infrared spectroscopy (IRIS) and leaf gas exchange systems we evaluated the isotope composition of transpiration and the rate of change in leaf water isotopologue storage (isostorage) when leaves were exposed to variable environments. In doing so, we developed a method for controlling the absolute humidity entering the gas exchange cuvette for a wide range of concentrations without changing the isotope composition of water vapour. The measurement system allowed estimation of ¹⁸O enrichment both at the evaporation site and for bulk leaf water, in the steady state and the non‐steady state. We show that non–steady‐state effects dominate the transpiration isoflux even when leaves are at physiological steady state. Our results suggest that a variable environment likely prevents ISS transpiration from being achieved and that this effect may be exacerbated by lengthy leaf water turnover times due to high leaf water contents.