New Zealand falcon nested in pine stands sized between 0.17 km2 and 24.14 km2. More falcon nests were located in small pine stands less than 4 km2 than in larger pine stands. However, there were more small pine stands than large pine stands available in the forest (Fig. 5.3), which must be accounted for when considering selection. Small stands less than 1 km2 were used less than expected considering their high availability (Fig. 5.3). When allowing for the difference in availability of pine stand sizes, there was no difference between the number of stands of each size available and the number of each size used for nesting by New Zealand falcons (Kolmogorov two- sample test K=0.77, n.s.) (Fig. 5.4), indicating that no particular sized pine stand was being selected.
Figure 5.3. The percentage of nests located in each stand area class in 2005 and the percentage availability of stands less than four years old in each area class in 2005.
Figure 5.4. Plot showing cumulative percentage nests against cumulative percentage area (km2) of all
stands in Kaingaroa Forest (2005/2006 breeding season only). Where a stands is defined as a discrete area of less than four years old.
5.4.4 Habitat and forestry management
Despite the relatively low variation in many habitat and forestry management variables between nest and non-nest sites, discriminant analysis revealed several variables that explain differences between nest and non-nest sites (see Appendix 1). Nest sites had a lower pine height surrounding them, had more cover over the scrape,
had taller pines at the stand edge nearest the nest (where a stand edge is the border between two pine stands differing in height by 4 m or more), andwere significantly closer to stand edges than non-nests. Further, compared to non-nest sites the nest site home ranges had a larger area of pines aged 20 years old or more and a significantly smaller area of pines between 4 and 9 years old. Nest sites had a mean pine height of 1 m, the mean cover over the scrape was 65 percent (ranging from no cover to 100% cover), and the mean heights of the pines at the nearest stand edge were 20 m (see Appendix 1). Over 60 percent of nests were located 100 m or less from the nearest stand edge, and over 90 percent were located 200 m away or less (Fig. 5.5). The type of cover over nest scrapes varied from those over non-nest scrapes (χ2 =43, d.f. 8,
P<0.0001), (see Appendix 2). The most common cover types over nest scrapes were pine logs and tree fern trunks (Dicksonia sp. and Cyathea sp.), but included thin plants of various species, tree fern fronds, pine stumps, pine branches and in one case a small bluff.
Figure 5.5. The distance to the nearest stand edge (a border of trees differing in height by at least 4 m) of the nests located in the 2004 and 2005 breeding seasons.
Pest controlwas carried out over most of Kaingaroa Forest during or before the study period. The most common control method employed was poisoning of plantation pests using 1080 poison (sodium monofluoroacetate). No significant difference was recorded between nest and non-nest sites in the time since 1080 was applied (P=0.29) (see Appendix 1). Nest sites and non-nest sites did differ significantly in the type of bait most commonly applied and the method of application. However, this difference
was largely a result of including the northern part of Kaingaroa Forest in the sample of non-nest sites. No falcon nests were located in the north and pest control was applied differently there. In fact, the north of Kaingaroa Forest differed from the south in several of the recorded variables, including pest control application method, bait type, soil, relief and rotation number (see Appendices 1 & 2). All of these variables are therefore confounded with location. Non-breeding pairs were recorded in the north of Kaingaroa Forest later in the study, indicating that falcons are likely to breed there in the future. We suggest therefore, that none of these variables are affecting falcon nest site choice, and the significant results are a result of confounding variables related to location.
For the other management variables measured, we found no significant difference between nest and non-nest sites (see Appendix 1), including herbicide type (desiccant and release sprays), fertilizer type and time since these were applied before the breeding season.
5.4.5 Breeding dispersal
There were 174 New Zealand falcons colour banded in Kaingaroa Forest during this study, and 28 previously banded by Wingspan Birds of Prey Trust. This included 28 adult males, 27 adult females, 73 fledgling males and 74 fledgling females. During the study, 63 banding recoveries were made, including 19 males and 44 females.
The mean distance moved by individuals between subsequent nest attempts was 0.91 km (n=50), ranging from zero to 4.24 km. Only two pairs remained to nest in the same nest scrape the following breeding season. One pair was recorded laying in the same scrape for three subsequent breeding seasons.
Table 5.2. Breeding dispersal of pairs between pine stand age classes between subsequent breeding seasons 2003 to 2005.
Stand age class movement (years) %
Moved to another stand of the same Zero to zero 19
Age One to one 6
Two to two 0
Three to three 0
TOTAL 25
Moved into a younger stand One to zero 8
Two to zero 6 Three to zero 2 Two to one 2 Three to one 0 Three to two 0 TOTAL 19
Remained in same stand in subsequent Zero to one 25
seasons One to two 23
Two to three 6
TOTAL 54
Moved to an older stand Zero to two 0
Zero to three 0
One to three 2
TOTAL 2
Fifty four percent of pairs nested in the same pine stand the following year. Forty four percent moved to a younger stand or another of the same age (Table 5.2). Only one falcon pair was recorded moving into an older stand between breeding seasons. Of those that moved into younger stands, 35 percent moved into stands that had not been planted or were only just planted the previous winter. Of those pairs that remained within the same compartment between breeding seasons, 25 percent remained to breed in one year old pines, 23 percent remained to breed in two year old pines, but only six percent remained to breed in stands of three year old pines.
Eighty percent of pairs remained together to attempt to breed in subsequent breeding seasons. In 12 percent of nest attempts the male of the pair changed between breeding seasons and in eight percent the female changed. In all but one case, the location of the individual that left the pairing was unknown. In this one case both individuals of the pair were found breeding with new partners. In no cases were both individuals in a territory replaced by a completely new pair the following breeding season.
5.5 Discussion