37

Notornis, 2022, Vol. 69: 37-44
0029-4470 © The Ornithological Society of New Zealand Inc.

New Zealand falcons (Falco novaeseelandiae) hunting
petrels at night and underground during the day
COLIN M. MISKELLY*
Museum of New Zealand Te Papa Tongarewa, PO Box 467, Wellington 6140, New Zealand
LOUISE McLAUGHLIN
Department of Conservation, PO Box 29, Te Anau 9600, New Zealand
ANDRE DE GRAAF
c/o Haast Postal Agency, 425 Haast-Jackson Bay Road, Haast 7886, New Zealand
Abstract: New Zealand falcons (Falco novaeseelandiae) routinely feed on burrow-nesting seabirds (petrels:
Procellariiformes) at several sites. As petrels are rarely present on the colony surface during daylight, and falcons are
considered to be diurnal hunters, there has been much speculation about how falcons are able to capture petrels. We
present evidence that New Zealand falcons are able to hunt petrels in forest at night, and also enter burrows during the
day to extract chicks. These are novel hunting behaviours for falcons, and further increase the broad range of hunting
strategies documented for New Zealand falcons. While these hunting methods may be used by only a few individual
birds, they can produce high prey-capture rates.
Miskelly, C.M.; McLaughlin, L.; de Graaf, A. 2022. New Zealand falcons (Falco novaeseelandiae) hunting petrels at nightand underground during the day. Notornis 69(1): 37–44.
Keywords: falcon, hunting, night, nocturnal, petrel, seabird, underground

INTRODUCTION
New
Zealandfalcons(kārearea,
Falco
novaeseelandiae) are versatile foragers compared toother falcon species (Seaton & Hyde 2021). Sevendifferent aerial hunting techniques were described
for them by Fox (1977, and in Marchant & Higgins
1993), combining methods used by short-winged
forest hawks (Accipitridae: Accipiter spp.) and opencountry falcons (Falconidae: Falco spp.) elsewhere
Received 1 September 2021; accepted 19 October 2021
*Correspondence: colin.miskelly@tepapa.govt.nz

in the world. New Zealand falcons can also extract
nestlings from tree-hole or crevice nests (Marchant& Higgins 1993), and they can hunt on the ground:they have been observed hunting for ground-levelbellbird (Anthornis melanura) nests and chicks
among tree roots on the subantarctic Auckland
Islands (Miskelly et al. 2020a). New Zealand falcons
on the ground have also been observed stalking
and catching skinks (Oligosoma spp.) on mowngrass on Takapourewa/Stephens Island in theouter Marlborough Sounds (AdG pers. obs.), andattempting to do so among sand dunes on Whenua

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Miskelly et al

Hou/Codfish Island (Jake Osborne pers. comm. to
CMM, 10 September 2021).
Falcons worldwide are generally regarded
as diurnal predators, relying on acute eyesight
to locate prey, often from great distances (Brown& Amadon 1968; Marchant & Higgins 1993;
del Hoyo et al. 1994). However, New Zealandfalcons have frequently been reported as having
consumed species of burrow-nesting petrels(Procellariiformes: Procellariidae, Hydrobatidae,
and Pelecanoididae) that visit their breedingcolonies only at night (Wilson 1959; Harrow 1976;
Chance 1992; Worthy & Holdaway 1995; Worthy
1997; Worthy et al. 2002; Worthy & Zhao 2006;
Hyde & Worthy 2010; Cuthbert 2017; Miskelly et al.
2019, 2020; Elliott et al. 2020). There has been much
speculation on how falcons are able to capture
these petrels, including suggestions that falcons
are catching birds out at sea, or catching birds that
arrive at the colony before it is fully dark, or birds
that depart late, when there is sufficient light forfalcons to begin hunting (Harrow 1976; Worthy &Zhao 2006; Hyde & Worthy 2010; Cuthbert 2017;
Elliott et al. 2020). We document two previously
unreported hunting methods used by New Zealandfalcons to capture petrels: hunting at night under
forest, and entering burrows during the day. Thesebehaviours further extend the diverse repertoireof hunting behaviours recorded for New Zealandfalcons.
STUDY SITES AND METHODSAll observations were serendipitous encountersor recordings made during other conservation
research, management, or leisure activities.
Evidence of New Zealand falcons hunting mottled
petrels (kōrure, Pterodroma inexpectata) in the middleof the night was obtained at two widely separated
colonies in Fiordland, and a falcon was observed
catching fairy prion (tītī wainui, Pachyptila turtur)chicks inside burrows on Takapourewa/Stephens
Island in the Marlborough Sounds. Observation
and recording methods are described under eachstudy site below.
Lake Hauroko‘Motukōrure’ islet (0.3 ha) lies 500 m south of
Mary Island in Lake Hauroko, eastern Fiordland.
It is usually free of introduced mammals andhad an estimated 530 mottled petrel burrows inDecember 2019 (Miskelly et al. 2021). Following
evidence of stoats (Mustela erminea) and then mice(Mus musculus) reaching the islet in mid-2020,
trail cameras were installed on the islet as partof a successful pest mammal incursion response.
Three cameras were installed on 28 May 2020, andthen replaced with a single ‘permanent’ camera(Browning Dark Ops Apex, model BTC-6HD-APX)
on 12 August 2020. This was the last date that
evidence of stoats was detected on the islet, with
two stoat corpses found in traps.
The single camera in place from August 2020
monitored activity over about 30 m2 of forest floor,
with the branches of 4–5 trees also close enoughfor large birds in them to trigger the motion-sensor.
The camera was set to record 10 seconds of video
whenever the motion-sensor was triggered. The islet
was visited again by Department of Conservation
staff on 9 October, 19 November, and 14 December
2020, and 29 January, 18 February, 1 April, 7 May, 11June, and 4 August 2021, with the SD card from thecamera removed and replaced on each occasion.
Mottled petrel corpses were searched for on thecolony surface, and either photographed or thecorpses retrieved to determine cause of death.
Any video clip with a falcon in it was classified
as ‘falcon activity’. Records of falcon activity
within 30 minutes of each other were considered
to be part of the same falcon visitation event. These
were classified as ‘day’ if between sunrise andsunset, ‘dusk’ during the hour after sunset, and‘night’ from then until an hour before sunrise. No
falcons were detected in the hour before sunrise.
All times are reported in New Zealand Standard
Time. Percentage moon disc illumination was
obtained from the website https://lunaf.com/
lunar-calendar, viewed 15 August 2021.
		 In February 2011, the first calls by mottled
petrels flying over the colony were heard 27–38
minutes after sunset (average = 33 minutes, n = 7;
Matt Rayner pers. comm. to CMM, 30 August 2021).
Anchor Island
An estimated 700 mottled petrel burrows were
found on the largest islet in Anchor Island Harbour
in Dusky Sound, Fiordland, in November 2016
(Miskelly et al. 2017). CMM camped on the islet on
the night of 27–28 February 2021, as part of a fourperson research team collecting viral swab samples
from mottled petrels and sooty shearwaters(Ardenna grisea). Direct observations of mottled
petrels and a New Zealand falcon were madebetween 2145–0110 h and 0415–0635 h.
Takapourewa/Stephens Island
AdG and Polly Hall were the Department ofConservation rangers on Takapourewa/ Stephens
Island at the northern tip of the MarlboroughSounds during 2012–15. A pair of falcons wasresident on the island, and successfully fledged two
chicks in each of the 2012–13 and 2013–14 breeding
seasons.
Takapourewa holds the world’s largest fairy
prion (Pachyptila turtur) colony, with an estimatedFalcons hunting at night and underground39

Table 1. Details of five occasions when a New Zealand falcon was filmed being active at night, or feeding on or
carrying a mottled petrel corpse. All footage was captured on a trail camera set within a mottled petrel colony on a 0.3
ha islet in Lake Hauroko, Fiordland, in 2021. Shading is used to highlight nocturnal activity by the falcon or falcons.
All times have been converted to New Zealand Standard Time. Lunar disc illumination is given as “% moon” under
Day/Night (see Methods).
DateTime (h)Day/Night

Description

15 Feb2010

Dusk

Falcon flies up to tree perch carrying petrel (windy conditions), then flies
further along perch, still carrying petrel. Many feathers on ground andbeing blown about

19 Feb2040

Dusk

Falcon drags petrel carcass in from left to front of camera, using one foot. It
proceeds to pluck the carcass and then feed over the next 17 min

25 May0028

Night
99% moon

Falcon on ground, walks towards camera, with feather stuck to beak thenpecks at something (out of camera, in foreground); 6 min later falcon walks
away from the camera, to edge of bank

7 June1818

Night
8% moonFalcon on ground, to the left near the camera. Moves off to left out of frame

4 Feb

0403

Night
49% moon

Falcon attacking petrel, flying from tree to ground; tussle for 3 seconds,
then falcon on ground looking away from petrel (which is out of sight)

1.4 million pairs (Craig 2010; Jamieson et al. 2016).
Fairy prions breed synchronously, with chicks on
Takapourewa fledging from late January to midFebruary (Miskelly & Gummer 2013). Before midJanuary, prion chicks were not seen outside of theirnatal burrows by day or night, unless their burrows
were flooded by an extreme rain event.
AdG was reading a book on the veranda of
the rangers’ house, in late December 2013, when
he made the direct observation of a New Zealandfalcon catching fairy prion chicks described below.
RESULTSNew Zealand falcon predation on mottled petrels
based on prey remains
Three beheaded mottled petrel corpses were foundon Motukōrure islet on 18 February 2021. Based onimages of these, Graeme Taylor, Chifuyu Horikoshi,
and Noel Hyde considered that they had been
killed by a falcon (pers. comms to LMcL). At least 10
petrel carcasses were seen on 1 April 2020, a freshcarcass was noted on 7 May, and 26 carcasses wererecovered on 11 June 2021 (these may have included
all the previous corpses recorded). Fourteen of themottled petrel corpses that were removed from theislet in May and June were confirmed as likely tohave been killed by falcons, either in the field or
during necropsy and skeleton preparation at Te
Papa (authors, pers. obs.). The corpses included both
adults and pre-fledged chicks.
Three sites where a falcon had plucked mottled
petrels were found on the islet in Anchor Island
Harbour during the evening of 27 February 2021.
However, the team was unaware of any falcons

being present on the 0.3 ha islet before they retired
to their tents at 0110 h.
Nocturnal hunting
Video evidenceVideo footage of a falcon (possibly a single adult)
on Motukōrure islet was captured in 75 video
clips during 53 falcon visitation events on 37
dates between 22 January and 7 June 2021. Videoevidence of the falcon or falcons being active atnight, and/or interacting with live or dead petrels,
is summarised in Table 1. These included sequencesof a falcon attacking an adult mottled petrel at night(4 February; Figs 1A & B), a falcon flying to a perch
carrying a petrel corpse (15 February), and a falcon
plucking a mottled petrel corpse (19 February;Fig. 1C).
		 Most of the falcon activity was during the day(75%), with 19% at dusk, and five video clips (three
events = 6 %) at night. These clips showed thefalcon (or falcons) as being active in the middle ofthe night: at 0403 h on 4 February 2021 (the attack
sequence described below), at 0028 h, 0029 h, &0034 h on 25 May 2021, and at 1818 h on 7 June 2021.
This last event was 1 h 6 min after sunset.
On 25 May, an adult falcon walked towards thecamera (Fig. 1D) and then pecked at an apparent
prey item on the ground that was too close to be in
the camera field of view. Six minutes later, the falcon
walked away from the camera. This date was one
day before full moon (and had 99% illumination);
however, local cloud cover conditions were notrecorded on any date.

40
A

Miskelly et alC

at 0628 h). The site where the kill occurred had
been visited multiple times earlier in the night.
The falcon scrambled up a sloping trunk in CMM’s
headlamp beam and flew out through the canopy.

Hunting underground
Direct observation
The falcons on Takapourewa used live prionchicks each year to teach their fledglings how tocatch prey in mid-air, and how to kill prey. The
D
adult female falcon was frequently observed
Bfrom late December to February carrying downy
prion chicks and calling to her fledglings, before
dropping the live prion chick for them to attempt
to catch. If they failed to catch the falling chick, it
was not retrieved, and the female would fly off tocatch another chick.
At c. 1500 h on an unrecorded date in late
December 2013, an adult female New Zealandfalcon landed near the rangers’ house on
Takapourewa, ran under a hedge, then emerged
Figure1.Two
A &frames
B) Twoframesa videoshowinga New
Figure1. A & B)
froma videofrom
showinga New Zealandfalconattacking asoon after with a prion chick. This was used for
Zealandattackinga mottled
petrelan hislet
inmottledpetrel onfalcon
an islet in
Lake Hauroko,
Fiordland,
filmed on
at 0403
on 4 February
a training session with the two fledglings nearby,
Hauroko,
Fiordland,
filmedat birds.
0403 Ah link
on 4toFebruary
2021.Lake
The brightspots arethe eye-shinesof both
the video clip is
but was soon dropped and lost in the long grass.
providedinSupplementarymaterials.
C)
ANew
Zealandfalconpluckingamottled2021. The bright spots are the eye-shines of both birds. A
petrellink
corpsean isletin LakeFiordland,
filmed at 2046 h on 19
FebruaryThe adult female returned to the hedge on two
toonthevideo
clipHauroko,
is provided
in Supplementary
ma2021.terials.
D) A NewC)
Zealandfalconwalking falcon
around atplucking
night at a mottled
petrel pecolony onfurther occasions, and each time she was observed
A New
Zealanda mottled
an isletin corpse
Lake Hauroko,
filmedHauroko,
at 0028 h on Fiordland,
25 May 2021. filmed
entering a prion burrow and disappearing out oftrel
on anFiordland,
islet in Lakeat 2046 h on 19 February 2021. D) A New Zealand falcon
site, before emerging backwards 5–10 seconds later
walking around at night at a mottled petrel colony on an
dragging a live prion chick with her beak. Once on
islet in Lake Hauroko, Fiordland, filmed at 0028 h on 25
the mown lawn by the house, the prion chick was
May 2021.
transferred to one foot before an ungainly running
take-off with the heavy load.
The two burrows that the falcon was seen toenter were close together (and near the site where
The moon was ¾ full on 4 February (49%the first of the three prion chicks was caught). One
illumination), when a falcon was recordedof these burrows was inspected by AdG. It had
attacking a mottled petrel (Figs 1 & B).1 The adulta wide entrance leading to multiple prion nest
petrel was likely leaving the colony before dawn
chambers, all of which were beyond the length of(it was 1 h 46 min before sunrise), and was moving
his arm.
rapidly downslope, partially obscured by theOn other occasions, the adult female wassurface topography. The falcon bounded downobserved emerging with a prion chick froma sloping tree trunk towards the petrel, and thenthe same patch of forest several times in quickattacked it largely out of camera view, below thesuccession, without the method of prion chick
crest of a low bank. Flailing wingtips were visible
capture being observed. However, the impression
for about 3 seconds, before the falcon re-appeared
was that she routinely entered prion burrows, as
facing away from where the petrel had apparently
there is no other way that she was likely to haveescaped downhill.
been able to catch the concealed prion chicks so
rapidly.
Direct observation
An adult New Zealand falcon was disturbed fromVideo evidence
a freshly killed (still warm) adult mottled petrel
The trail camera on Motukōrure islet recorded aon the islet in Anchor Island Harbour at 0440 h on
falcon walking on the ground on 45 occasions (85%28 February 2021. It was a still, clear night with aof visitation events) between 22 January and 7 Junefull moon (100% illumination), although it was
2021. No falcons were detected during the previous
dark under the dense Olearia canopy (sunrise was[1] See also video supplementary material: https://www.youtube.com/watch?v=bKej-T20pwo

Falcons hunting at night and undergroundeight months or the succeeding two months.
Although the bird was not seen inspecting or
entering a burrow, there were no burrow entrances
within the field of view – the camera was focusedon a bait lure (intended to attract stoats) above apatch of flat ground with little ground cover.
DISCUSSION
Falcons hunting at nightNocturnal hunting by falcons away from artificial
lights is rarely reported. The low incidence of
falcons being recorded on video at night on
Motukōrure Islet (plus the single observation from
Anchor Island) indicate that nocturnal hunting may
be a rare behaviour, with night activity focussed onbright moonlit nights. However, it is possible that
the Motukōrure falcon had favoured nocturnal
hunting sites (e.g. areas with a more open canopy)
elsewhere on the island, where activity would nothave been recorded by the single camera present.
The only other report of a New Zealandfalcon hunting in the middle of the night that weare aware of was told to Noel Hyde by Mr Robin
Bagge of Tauranga, on 28 March 2009 (Noel Hydepers. comm. to CMM, 22 July 2021). Robin Bagge
worked for the New Zealand Forest Service andwas a keen hunter. In 1978, while deer hunting with
Stan Lowe in the middle reaches of Horomanga
Stream, Murupara, they heard the squawking of abird at 0200 h. Robin shone his spotlight up a tree
and saw a falcon (presumed to be a male, basedon its size) holding a still alive, flapping sacredkingfisher (Todiramphus sanctus). When questioned
as to how bright the night sky was, he replied that
he never hunted on a full moon, suggesting that the
kingfisher had been caught at much less than 100%
lunar illumination.
Potts (1882: 44) reported that “On Banks
Peninsula we have observed it [New Zealandfalcon], in the wintry month of June, hawking by thelight of the waning moon, ere the little owl [likely
Ninox novaeseelandiae], warned by the coming ofday, has retired to the dim obscurity of its roost in
the decayed tree.” However, the reference to an owl
going to roost indicates that this observation was
pre-dawn rather than during complete darkness.
Many falcon species hunt in dim light aftersunset and before dawn (Brown & Amadon 1968;
Ratcliffe 1980; del Hoyo et al. 1994); however, wehave found limited evidence of falcons hunting
by natural light in the middle of the night. The
numerous accounts of peregrine falcons (Falco
peregrinus) hunting at night were mainly of birds inurban settings using artificial light to locate theirprey (e.g. Rejt 2004; DeCandido & Allen 2006; Kettel
et al. 2016; Time 2016). Similar behaviour has beenreported for common kestrels (F. tinnunculus), lesser

41

kestrels (F. naumanni), sooty falcons (F. concolor),and Eleanora’s falcons (F. eleanorae) (Sachslehner
1996; Negro et al. 2000; Gschweng 2013; Buij &Gschweng 2017).
Satellite-tracking or GPS data loggers haverevealed some lesser kestrels and Eleanora’s
falcons to be active at night in areas away from
artificial illumination, particularly when moon
disc illumination was >60% (Gustin et al. 2014;
Buij & Gschweng 2017). However, the nearest
comparable accounts that we have found of falcons
hunting at night under natural light (or at sites
with little artificial illumination) were two studies
of peregrine falcons hunting seabirds at theirbreeding colonies, and one account of a duck being
taken.
Wynn et al. (2010) used infrared cameras todetect nocturnal predation of Balearic shearwaters(Puffinus mauretanicus) by a peregrine falcon onbare ground at a cave entrance on the island ofMenorca. At least 18 shearwaters were killed overtwo breeding seasons, at a rate of about 0.5 kills
per night over a 2-month period, with most attacks
occurring on moonlit nights (Wynn et al. 2010).
It is unclear whether the cave entrance received
artificial illumination, although the authors
mention a tourist development nearby, and that
“Artificial lights from these developments may
assist night hunting Peregrines” (Wynn et al. 2010).
Collins et al. (2014) also used infrared cameras,
installed at a black-legged kittiwake (Rissa
tridactyla) colony on a cliff on Puffin Island, Wales,and detected predation of kittiwake chicks bya peregrine falcon. The two predation events
captured by the camera occurred 53 mins and48 mins before sunrise, 2 days apart: “It would
not have been completely dark during predation
events, thus it is possible that the peregrine wasusing the low-light conditions to enhance its chanceof predation success” (Collins et al. 2014).
Hirata et al. (2013) reported a peregrine falconthat killed a mallard (Anas platyrhynchos) 40
minutes before sunrise, in an area with minimal
artificial lighting in Hokkaido, Japan (Hirata et al.
2013). The snow-covered open ground may havefacilitated detection of the dark-plumaged prey inthe low light conditions.
		 In all three situations described by Wynn et al.
(2010), Hirata et al. (2013), and Collins et al. (2014),
the peregrine falcons were hunting in open,
uncluttered environments, and may have beenutilising artificial light, or light from the sun in
the hour before sunrise. These circumstances wereunlike the complex environments under dense
canopy where we recorded New Zealand falcons
attacking or feeding on mottled petrels more than
100 minutes before sunrise.

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Miskelly et al

Falcons entering burrows to catch seabird chicks
Although a falcon was observed entering petrel
burrows on a single date only, we interpret theregular presence of a falcon on the ground at a dense
mottled petrel colony during daylight (as detectedby video) as circumstantial evidence that the bird
was searching for petrel chicks inside burrows.
The falcon was recorded only during the nestling
period for mottled petrels (Warham et al. 1977), andit spent much of this time walking over the colony
surface. The high recording rate (a minimum of 37days over 4 months) is noteworthy, given the tiny
patch of forest floor in the camera field of view. The
highest density recorded for falcons on mainland
New Zealand is about one pair per 900 ha (Seaton& Hyde 2021), although the Takapourewa falcons
probably confined their hunting to the 150 ha island
while breeding. Falcons have never been recorded
nesting on 0.3 ha Motukōrure islet; however, atleast one adult falcon visited the islet sufficiently
often in 2021 to be detected on a single trail camera(viewing less than 1% of the islet) on at least 27%of days during the mottled petrel nestling period.
When combined with the recovery of at least 26
mottled petrel corpses (including of pre-fledged
chicks) during this time, and the apparent absenceof stoats on the islet in 2021, we suspect that thefalcon was routinely entering burrows during
daylight to extract petrel chicks, as observed on
Takapourewa.
We have not found any published accountsof falcons hunting underground. However, Noel
Hyde (pers. comm. to CMM, 23 July 2021) describeda trained New Zealand falcon entering a burrow
when in pursuit of a rabbit (Oryctolagus cuniculus):“Some years ago, a female bush falcon I was flying
perched on a post. We noticed it started head bobbing andfocussing intently on a rabbit about 200 m away. The
falcon quickly launched into a direct flying attack, andas it closed in, at the last moment the rabbit bolted. The
rabbit sprinted across the paddocks about 150 m withthe falcon in hot pursuit about 3 m behind. The rabbit
disappeared down a burrow, and to our amazement thefalcon followed the rabbit into the burrow at speed. On
running over and looking in, the falcon was nearly an
arm-length down the burrow, with the young rabbit
firmly in its clutches. I had to reach in and gently wriggle,
and pull the falcon out with her still firmly attached to
the rabbit.” This active pursuit of fleeing prey into aburrow differs from falcons hunting petrel chicks,
which remain stationary in a nest chamber at theend of a long burrow during daylight, and only
begin to emerge (at night) in the week or so before
fledging (Warham 1996).
Falcon predation of petrels in Fiordland
Hunting of mottled petrels by falcons on
Motukōrure islet has been sporadic, rather thancontinuous, over the past 47 years, suggesting that
it is self-acquired behaviour by perhaps only two
individual birds. The first report of mottled petrelson the islet was by Tom Neave and his daughter
Rosemary in May 1974 (Wynston Cooper pers.
comm. to CMM, 28 August 2021). The 2–3 partial
skeletons that Tom Neave forwarded to the National
Museum via the Wildlife Service for identification
were considered by curator Sandy Bartle to havebeen killed by a falcon (Wynston Cooper ibid.).
Wynston Cooper monitored the Motukōrure
mottled petrel colony during 31 visits between 1982
and 1987, and never observed a falcon on the islet(Wynston Cooper ibid.). Similarly, no evidence of
falcons, or falcon predation of petrels, was detectedduring at least annual visits to the islet between
2008 and 2020 (Colin Bishop and Jenny Rickett
pers. comm. to CMM, 30 August 2021). Matt Rayner
camped on the islet for 26 days between 2009 and2011; he found no evidence of predation, but heard
a falcon calling over the island on a single occasion(Matt Rayner pers. comm. to CMM, 30 August 2021).
Evidence of falcons having fed on at least ten
broad-billed prions (Pachyptila vittata) was found atfive colonies on the outer Fiordland coast during
2017 and 2019 (Miskelly et al. 2019, 2020b). This
included an adult falcon that was disturbed froma freshly killed (and mostly consumed) adultprion on an islet off the south coast of Passage
Island in Chalky Inlet at 1700 h on 23 November
2017 (CMM, pers. obs.; photograph in Te Papa blog
‘Seabird discoveries in remote southern Fiordland’,
published 5 December 2017). We were unable
to determine how these prions were captured.
However, we did not encounter any on the surface
or flying over any of the 28 Fiordland colonies
surveyed during daylight in 2016–2020 (Miskelly et
al. 2021; CMM pers. obs.).
While the multiple records of New Zealandfalcons feeding on broad-billed prions at theirbreeding colonies in Fiordland indicate that falcons
may be hunting at night or underground, there areother ways that they may have captured the petrels.
These large-headed prions are prone to gettingcaught by the neck in tree forks (e.g. illustrationin Cemmick & Veitch 1985: 45), and it is possiblethat falcons were attracted to the flailing wingsof trapped prions after day-break. We consider it
unlikely that falcons were catching mottled petrels
or broad-billed prions at sea before dark (e.g. as
Clunie 1976 reported for a peregrine falcon hunting
collared petrels Pterodroma brevipes and tropical
shearwaters Puffinus bailloni in Fiji). We never saw
these petrels from land before complete darkness,and the islets that they breed on are tiny specks
near much larger landmasses with numerous
potential perches or landing sites for falcons (i.e.
it is unlikely that falcons returning from the sea

Falcons hunting at night and undergroundcarrying a petrel would land on a Fiordland petrelcolony to feed on it).
Apart from Fiordland and the MarlboroughSounds, there are few other places where New
Zealand falcons currently co-occur with densecolonies of breeding petrels. Petrels of six species
formed a major portion of the diet of New Zealandfalcons on Adams Island in the subantarctic
Auckland Islands (Hyde & Worthy 2010; Elliott etal. 2020; Miskelly et al. 2020). Harrow (1976) andCuthbert (2017) reported New Zealand falcons
feeding on Hutton’s shearwaters (Puffinus huttoni)in the Seaward Kaikoura ranges and suggested
that they were catching departing birds in thehalf-light of dawn. When combined with ourobservations, these accounts from Kaikoura andthe Auckland Islands reveal that New Zealandfalcons readily exploit burrow-nesting seabirds asa food resource when present, and that they use
a variety of hunting techniques to capture them,including hunting at night, and entering burrows.
Studies using monitoring devices attached to
falcons (including GPS, light sensors, and tri-axial
accelerometers) and a network of trail cameras
could be used to determine how often each method
is used by individual birds and local populations,and the proportion of petrel burrows inspected orentered.
ACKNOWLEDGEMENTS
CMM
thanksRebecca
Frenchfortheopportunity to visit Anchor Island in
February–March 2021. The Fiordland seabird
colony surveys undertaken between 2016 and2020 were funded by Te Papa and the Departmentof Conservation. Many thanks to Noel Hyde(Wingspan National Bird of Prey Centre) for
providing unpublished reports of unusual hunting
behaviour by New Zealand falcons, and for alerting
us to the published account by Thomas Potts. We
thank Jean-Claude Stahl (Te Papa) for preparing
still images from video clips, and Wynston Cooper,
Colin Bishop, Jenny Rickett, Matt Rayner, andJake Osborne for information on mottled petrels
and New Zealand falcons on Motukōrure islet
between 1974 and 2020, and falcons on Whenua
Hou/Codfish Island. This manuscript was greatly
improved by comments received from Ralph Buij,
Noel Hyde, and Craig Symes.
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