Where the future sits

Monitoring female behaviour & influencing nest success.

While the estimated number of individual males booming is important as a population index, what is also important is identifying and supporting females to achieve nest success because that’s where the future sits.

We have low recruitment rates (chicks reaching adulthood) for bittern in New Zealand and this, our fourth and final program – ‘Where the future sits!’ -addresses this crucial gap.

Background – Looking at the UK

(The Bittern in Europe– Survey and monitoring, BB July 2024)

We have looked to the UK who have increased the population of their Bittern with similar needs as ours to see what they have done to help detect females and nest success. The UK estimated only 50% of sites that have males booming showed evidence of nesting females.

Female nesting habitat selection seemed to follow a criteria which is reported to be a combination of being able to conceal their nest (density of habitat), proximity to feeding areas (higher fish biomass), and water depth (in vegetation where deeper water was maintained into the driest parts of the year).

Almost 20 years ago the UK established annual monitoring to estimate the number of nesting females. This estimate was achieved through what is described as time-consuming watches over sites with booming males. Watches involved continuous watching over 5 hours at least once every 10 days. Records were kept of any sign of female nesting behaviour (Bittern movements ie foraging flights, courtship behaviour and interactions).

The results were estimates, as there are a number of factors that bias them. For example, sites that were intact, where a female could walk to find food rather than fly, had low detection rates and nests where incubation failed produced less records (a result in itself).

In recent correspondence with the UK they found that this method of detection reduced in its efficacy as quality breeding habitat increased eg. where females could walk to find food in close proximity to the nest rather than take foraging flights.

Detecting nests using thermal drones

Like us the UK are now using thermal drones to detect females in nests and revisiting the nests to keep an eye on progress. Their program is just being developed around this while ours, under the careful guidance of DOC has been underway for some time and we anticipate a protocol to be published in the near future to help increase the nationwide capacity of drone operators (who may be DOC, Regional Council or other contractors). nb a permit is required to fly over a threatened species like bittern regardless of land ownership.

However drone operations can be expensive, time consuming and when using thermal cameras, are limited in time (need to be conducted at first light, cooler days to get enough contrast between heat of a bittern/nest and the air temperature).

In addition to this drone operations are not always possible (because of aviation fly zones) or vegetation that insulates the bittern from being able to be detected (eg. thick raupo).

We see this program supporting drone operations, in that it will help to pre-qualify nesting sites for further possible investigation.

How you can help

Our program helps people to identify and record female nesting behaviour, to help qualify nesting sites for potential further investigation and to provide further support to influence nest success.

If you have wetlands/ a wetland project that meets the following criteria we would love to hear from you-

evidence of male bittern booming and site occupancy (results from boom monitoring will provide this evidence).
a wetland that is able to be viewed passively without disturbing Bittern movements from a hide or a vantage point.
a team of people who are able to commit to time to watch (5hrs at least once every 10 days) and record their results for the duration of the breeding and chick raising period (from approximately mid August to mid March – or pulse when results consistently show no results for 20 days or more)
the capacity and capability to provide extra support/take action (see below) when females or nests are detected.
the ability to fund training at $300 plus GST(see below)

Full training is provided.

You will also be provided with a field sheet to record your observations and little else other than a clipboard, pen/pencil, binoculars, a good attention span and enough sustenance to get you through 5-hrs from pre-dawn is required!

We dont have funding for our programs so we ask groups we work with to cover our costs and charge a program fee which is a minimum of $300 plus GST (for a full or part day, is invoiced from our GST registered & registered charitable trust. (please note up to 3 events can be run in one day to optimise this eg training +school visit +community workshop/hui!)

How can we help influence nest success

The female looks after the nest and raises the chicks on her own. This makes the female (who is already smaller than the male and less able to defend herself) more vulnerable.

While the female is away from the nest getting food, her eggs and chicks are also more open to predation.

By supporting the female to reduce the time she is away from the nest and stopping predators from getting to her nesting area we may be able to positively influence nest success.

‘Support’ could include a combination of

ensuring fish or a source of food is abundant and as close to the nest as possible.
fine tuning your predator control,
monitoring and controlling pest invasions without causing any disturbance during the time a female is nesting or raising her young
ensuring fish or a source of food is abundant and as close to the nest as possible.

Please contact us if you have any questions or are interested in participating in this vital work.