5.2. Body condition and morphology of nesting hen pheasants

5.2.1. Effects of supplementary feeding on body condition

Data presented in III and V show that hen pheasants which were provided supplementary grain through spring had significantly larger fat reserves than hens in areas where feeding had ceased at the end of the shooting season. These are the first published studies demonstrating the effects of spring supplementary feeding on fat reserves of free-living pheasants, though improved winter body condition through supplementary feeding has been shown by Bogenschutz et al. (1995). Many of the hens collected from unfed plots and sites had negligible fat reserves. The levels of fat reserves of hens on fed sites in April (III & V) were comparable to fat reserves typically found in hen pheasants in winter (Carroll et al. 1997, Draycott 2002), when supplementary feeding is common (Robertson et al. 1993a, III). In the absence of spring supplementary feeding, fat reserves were reduced by 40% to 50% of their winter levels (III, V). Leif & Smith (1993) showed that bobwhite quail (Colinus virginianus) which consumed low energy foods were also unable to accumulate as much body fat as bobwhites which consumed high energy foods. Given that nutrient requirements increase during the pre-nesting period (Wise 1994) and that pheasants use up most of their existing fat reserves during incubation (Breitenbach & Meyer 1959), it is likely that many of the unsupplemented birds were under nutrient stress going into the nesting period. The body mass of both fed and unfed birds increased significantly between February and April, (III). Therefore, body mass measurements alone, would provide an inaccurate estimation of hen body condition in spring. The increase in mass was due primarily to the presence of eggs in the body cavity (III).

Fat reserves were higher on wild sites than on released bird sites (V). This could be due to habitat differences between these types of sites. For example, on sites where there is an emphasis on wild bird management, there is likely to be a higher level of natural food availability due to better quality habitat provision as these sites are reliant on the productivity of the wild population. Without this positive management, natural availability of grains and seeds in spring on modern farms is very low, (Campbell et al. 1997, I). It is also possible that differences in fat reserves between wild and released birds was due to morphological and physiological factors caused by rearing birds on commercial foods (Putaala & Hissa 1995, Liukkonen-Anttila et al. 2000). Breast muscle mass was not influenced by supplementary feeding (III,V). Breast muscle mass is often used by researchers as an indicator of total body protein which is an indicator of body condition (Brittas & Marcström 1982, Tompkins et al. 2000). The fact that there were differences in fat levels, but no differences in muscle protein levels between sites is indicative of a diet deficient in high energy foods rather than a deficiency in high protein foods, confirming the findings in I and II. There was a reduction in breast muscle of hens in supplemented and unsupplemented plots between February and April (III) possibly because of physiological changes caused by season or reproductive state. Previous authors have noted losses in carcass protein during egg laying in other species including American coot Fulica americana (Alisauskas & Ankney 1985) and lesser black-backed gulls Larus fuscus (Houston et al. 1983).

5.2.2. Parasites

It has been postulated that supplementary feeding via hoppers may lead to increased incidence of parasites and disease due to the concentrating effect of feed sites (Lehmann 1984, Guthery 1986, Landers & Mueller 1986). Pennycott et al. (1998) provided evidence that supplementary feeding of passerines in winter may increase their vulnerability to infectious diseases. In Britain, spring parasite burdens in pheasants are often high (Draycott et al. 2000). Burdens of the nematode parasite Heterakis gallinarum of hens collected in April were high (V) compared with winter burdens (Robertson & Hillgarth 1993). However, there were no negative effects of H. gallinarum, S. trachea or Capillaria sp. on fat or muscle mass (V) implying that parasites did not adversely affect body condition. The concentration of birds at feed hoppers did not pre-dispose birds to more disease as there were no differences in parasite burdens between birds collected from sites where supplementary feeding continued into spring and sites where feeding ceased after the shooting season (V). Indeed, siting hoppers 50-75 m apart so there is sufficient for one hopper per cock territory (III, IV & VI), should help reduce concentration of birds at each hopper to just the territorial cock and his harem of hens.

5.2.3. Effects of supplementary feeding on digestive tract morphology

Breitenbach et al. (1963) noted that during long periods of adverse nutrition, hen pheasants became more efficient at digesting food because they increased their gut length and decreased alimentary motility. There was no difference in gizzard mass or caecal length between hens in fed and unfed plots (III). However, there was an increase in size of gut structures between February and April (III), revealing the elasticity of intestinal organs and how quickly they respond to changes in diet. An increase in gizzard mass and intestinal length is a common response of birds feeding on a bulky and fibrous diet (Thomas 1986), and has been shown in several game species including red grouse (Lagopus lagopus scoticus) (Moss 1972), Japanese quail (Coturnix coturnix japonica) (Savory & Gentle 1976), rock partridge (Alectoris graeca) (Paganin & Meneguz 1992) and capercaillie (Tetrao urogallus) (Liukkonen-Anttila et al. 2000). Captive rearing normally requires birds to be fed a commercially produced pelleted food which has a much lower fibre content than natural food (Liukkonen-Anttila et al. 1999). Feeding pelleted food can result in smaller gizzards and shorter intestines and caeca in grey partridges (Putaala & Hissa 1995). The abrupt change from a commercial to a natural diet after release can affect the ability to utilise nutrients from foods available in the wild for several weeks (Duke et al. 1984, Liukkonen-Anttila et al. 1999). However, the pheasants analysed in III had already spent at least 6 months in the wild before food supplementation had ceased and should have at least partially adapted to a wild diet. Similarly, the fact that the birds were also foraging on natural foods (II) with a higher fibre content probably ensured that their gut structure had to some extent already adapted to a wild diet. Therefore, the data in III suggest there is a natural change in the morphology of the gut during spring due to changes in diet. Indeed, more wild seeds and less grain were present in April compared to March (II). Seasonal changes in length of digestive tract have been noted in other game species including spruce grouse (Dendragapus Canadensis) (Pendergast & Boag 1973) and willow grouse (Lagopus lagopus) (Pulliainen & Tunkkari 1983). The cessation of supplementary feeding at the end of January probably initiated an increase in digestive efficiency by pheasants, but this increase may not have been sufficient for fat reserves to be maintained when availability of energy rich food groups were low (I & II).