*1 No Hunting in Spring
*2 Includes disturbances from recreational boats, sport fishing and researchers.

In contrast to the spring, there were fewer disturbances during the fall (Table 8.1), primarily because birds were more highly concentrated and the amount of commercial fishing had declined by that time (Table 8.2). The reduced frequency of disturbances can also be attributed to the fact that hunters, unlike commercial fisherman, were less likely to travel near large rafts of waterfowl, which generally were located in the middle of the Inner Bay. However, hunters were occasionally observed harassing rafts of birds, apparently in an attempt to increase shooting opportunities. While fewer disturbances were recorded during the fall, birds generally flew further and for longer periods (Table 8.1), while some birds left the Inner Bay altogether.

Prior to, and since the 1970s, the proportion of diving ducks using the Inner Bay at Long Point (relative to the rest of Long Point and the adjoining lakeshore area) has increased during spring and declined during fall (Figure 8.48 and 8.49). Apparently, even though disturbance rates were much lower in fall on Long Point Bay, Canvasbacks, Redheads, and Lesser and Greater Scaup have altered their daily activity patterns during fall prior to and since the 1970s. Diving ducks tend to leave the Inner Bay (a preferred feeding area) during the day, and concentrate on less productive or sub optimal areas along the southern shore of Long Point on the open waters of Lake Erie; birds are regularly observed making flights into the Inner Bay in the evening and returning to the Lake in the early morning. This is not exceptional, as several studies have reported that waterfowl respond to daylight disturbance by feeding at night (Thornburg 1973; Pedroli 1982; Takekawa 1987). As fall migrating waterfowl are not constrained by the need to acquire reserves for reproduction, and their life history strategies do not necessitate prompt arrival on wintering areas, spending the day on the Lake and limiting quality feeding opportunities to nocturnal foraging bouts on the Inner Bay is probably a suitable nutritional tactic in fall. However, if birds are unable to find sufficient food in the lake, some may not acquire levels of fat that they require for further migration. This seems possible because 1) birds may forage less efficiently at night, 2) birds may require more time to obtain the nutrients required to store sufficient body fat than that afforded during nocturnal foraging bouts, and 3) the more inclement micro-climatic conditions on Lake Erie compared to the bay would increase energetic and possibly, thermoregulatory costs. Another potentially adverse effect of limiting waterfowl access to preferred food sources may be decreased survival rates, which is caused by birds remaining at Long Point longer and foraging under suboptimal conditions, or by birds being forced by freeze-up to leave the Long Point area without sufficient nutrient reserves.

Although generally fewer birds were disturbed during spring, rates of spring disturbance at Long Point were substantially higher than during the fall, and they were also much higher than has been reported for waterfowl staging in other regions (Korschgen et al. 1985; Kahl 1991; Havera et al. 1992). This may be problematic as spring disturbance may have greater impact on migratory waterfowl populations than does autumn disturbance (Kahl 1991). Spring migrating waterfowl incur the additional burden of acquiring reserves for reproduction which are over and above the fat that they must accumulate to satisfy costs of migration. Also, spring migration is generally more abbreviated than the fall flight, as birds must arrive on breeding areas in time to complete reproduction and wing molt before fall migration. Consequently, birds have limited time to acquire nutrient reserves during spring migration. I suggest that the nutritional and temporal constraints of acquiring the reserves necessary for migration and reproduction inhibit waterfowl from relocating to the lake, despite high rates of human disturbance. In other words, high present and future nutritional costs probably oblige birds to forage intensively during the day and night (see Petrie and Petrie 1998). Adverse spring weather conditions, and the fact that Lake Erie is sometimes partially or wholly ice-covered during spring migration, probably also prevent waterfowl from making regular daily movements to the lake. Consequently, when rates of human disturbance surpass some critical threshold during fall, birds are capable of relocating to the lake during the day and returning to the Inner Bay at night to feed. In contrast, when the spring critical threshold is exceeded (which would differ from the fall threshold), nutritional, temporal, and meteorological constraints apparently discourage birds from relocating to the lake. At this critical point, birds are probably forced to vacate the Inner Bay for other areas with abundant food sources and limited human interference; the premature departure of waterfowl in response to human disturbance is well documented on wintering as well as staging areas (Hume 1976; Bell and Austin 1985; Edwards and Bell 1987). That food resources in spring may be less abundant (Korschgen et al. 1988) and of lower nutritional quality (Takekawa 1987) than in fall also suggests that repeated and constant disturbances may be having a significant impact on nutrient reserves in staging waterfowl.

Spring and fall disturbance on the Inner Bay may cause some foraging areas to be underutilized, which ultimately would reduce the carrying capacity of the Long Point area for staging waterfowl (Tuite et al. 1983; Kahl 1991). Also, even if birds compensate for heightened energy costs of disturbance-related increases in flight time, this would increase their daily energy intake and thereby further decrease the carrying capacity of Long Point's wetlands. For example, Korschgen et al. (1985) estimated that the 5.2 disturbances per day experienced by waterfowl on the Upper Mississippi River would increase the daily energy requirement by an equivalent of 23 grams (dry weight) of American wild celery buds (Valisineria americana).

Dabbling ducks tend to prefer shallow marsh areas and generally do not use the Inner Bay or south shore of Long Point to any degree. Consequently, the disturbance study performed by LPWWRF does not pertain to these species. However, the aerial waterfowl surveys conducted by CWS and LPWWRF during the 1970s, 80s and 90s provide some insight into the change in distribution of dabbling ducks at Long Point during that time. Dabbling duck use of the marsh areas associated with the Inner Bay has increased during the spring since the 1980s (Figure 8.50), whereas there has been a decreasing fall trend in dabbling duck use of the Turkey Point Marsh (Figures 8.42 and 8.51), Big Creek Marsh (Figure 8.43), Long Point Management Unit (Figure 8.44), and the Long Point Company Marsh (Figure 8.45) since that time. Conversely, there has been a fairly substantial increase in the fall dabbling duck use of the LPNWA (especially Bouck's Pond) since the early 1980s (Figure 8.46 and 8.51). Interestingly, the LPNWA was designated as a National Wildlife Area 1979 and all duck hunting was stopped in the area at that time. Therefore, I suggest that, since there has not been an increase in the number of hunters at Long Point since the 1980s e.g., no increase in hunting disturbance (Figure 8.56 and 8.57), the LPNWA is providing a sanctuary, particularly for dabbling ducks, and that this has simply permitted a change in the fall distribution of these species at Long Point since that time.