Thread by @ecoevoenviro

What do you know about the productivity and harvest of wild waterfowl? The biology of it is in some ways poorly known in Europe - but we can look at the USA first to see what they have found #ducks #conservation #utilitarian #thread (Credit: I.Acarpentier) /1

The USFW has invested in a wild duck biology research program - state funded - linked to income from hunters permits - but culturally subsidised - since at least the 1950s and from 1952 also studied hunter behaviour and success fws.gov/birds/get-invo… /2

Lets cut straight to the chase - and lets study mallards - the model on which all other adaptive harvest hunting decisions are made in the USA (possible because they dont waste time and effort on releases but invest in habitat on a continental scale - listening everyone 😇/3

The NAmer Adaptive Harvest model for waterfowl is a long running model - this thread is not about the benefits it has for investment in wetland habitats (but it does - the utilitarian conservation model) - its about population ecology and demography /4

We could look at any range of species or ducks or geese - but will focus on ducks for now - and stick to stats for mallard - but you could look at any species the same way - so to get started - the National state agencies survey waterfowl and water levels by plane and on foot /5

The main info is the aerial survey and wetland conditions - better conditions and based on all the data and surveys since 1950s they can predict better waterfowl productivity - dryer springs however mean less ducks and tighter harvest rules the following winter (credit USFW) /6

How many mallards - well in 2018 and 2019 - somewhere around 9-10 Million breeding birds in NAmer - with about 38-41 Million breeding ducks in total. The European population is estimated at 2.8-4.6M pairs, which equates to 5,700,000-9,220,000 mature individuals (IUCN) -similar /7

Harvest surveys and extensive capture mark recapture studies from well funded ringing programs give us information on hunting and natural mortality of ducks - and NAmer hunters harvest a great deal of wild ducks - 10.3Million ducks in 2018 and 9.7Million in 2019 /8

But we need to think about breeding productivity before we get to think about what harvest rate this might be - because those breeding pairs of ducks - they have baby ducks 😍 - photo Alain Audet /9

Back to Mallards - so using water conditions for predictions and then age ratios for productivity estimates - across 2017-2019 - Those 9-10M NAmer mallards produced 1.0-1.06 fledged young per adult - so flying south in winter is 18-20 Million mallards ducks.org /10

The data is all here at this link or from this site so please do check it out fws.gov/birds/surveys-… - of those Mallards - how many are harvested - across US and Canada - 3.36Million mallards were harvested in 2019 representing c18% of the population (photo Paul Sharp) /11

Taking account of the productivity is important - without it you assume harvest is much higher than it is - you cant take Breeding pairs estimates for European ducks and throw bag statistics at them - not least because of rear and release (photo G Catley) /12

In Europe we have poor breeding census data - but we do have excellent data from some regions. In general most dabblers are doing well - but climate change is having a big effect on their distributions - especially on these beauties (from wiki) /13

Given imperfect data, lack of national or international harvest management program for migratory w'fowl- and given climate change driven shifts - site managers and regulators (yes you @NaturalEngland) are starting to get jittery about effects hunting could have on "sites" /14

What we know- for hunting to effect a population the harvest rate in a winter must (short term) reduce the breeding population * breeding output the following spring or (long term) as short term but have significant demographic effects such as in time will reduce productivity /15

For local hunting to affect the local wintering population on a local site - even making erroneous but simplifying assumptions about turnover, foraging flight ranges etc relative to where hunting is conducted - the mortality dosn't affect the local population directly (Bauer) /16

After thinking about the life cycle and productivity - lets examine the situation in the UK where we don't have great data on hunting bags and we don't regulate hunting bags unless its on, over or near protected areas where it tends to be tightly regulated anyway (my photo) /17

Back to Mallards - in the UK/Europe the no. of mallards reared and released has increased 7 fold over the last 50 years - its not really hunting - its most often commercial shooting - albeit we accept their is some spillover into "wild" bags - its not into "wild" populations /18

Back to Mallards properly- we know from Norway, Sweden and Finland that wild migratory mallards are doing well - productivity is stable or increasing across recent decade (e.g. studies by Poysu, Gunnarsson, Elmberg) -but we know that they are not coming to the East UK as much /19

Breeding Mallard in the UK is currently listed as "Amber" - that means it has a warning. Breeding mallard in the UK has a 50 year rise of 150% - it was still increasing 25yo but that has slowed to a -6 and -3% decline most recently - in England those numbers are 180,21,-10,-5 /20

Mallard are doing quite well - IUCN thinks so too saying they are increasing Globally and in the US/Canada and the aforementioned studies from their northern wild breeding range suggest the same - finally what about the survival rates of European Mallards compared to US /21

Nearly there - just "site" issues to go - so survival - well there are lost of great estimates from the USA so go look but here is a radio tracking study in the Illinois area in 2008-2010 with annual adult survival of 0.39-0.62 - compares to 0.57-0.67 on the BTO website /22

Given all this - it seems to me that while we do have a climate change issue of range shifts - mallard hunting mortality in the flyway does not appear to be too high - despite being high in the UK (c900,000 - NB most are released - see Aebischer) - they still do well /23

Recap - high BBS in UK - some recent declines - high and stable pop in N Europe - productivity stable/increasing - survival estimates similar to USA where increasing - models (Gunnarsson) predict same in Europe - but UK site managers and regulators complaining about hunting /24

I really struggle to understand both the narrative and the quality of the population and numerical ecology in the complaints I have seen - but as I cant share them - you will have to take my word for it /25

Lets try to put ourselves in the shoes of a regulator or responsible person - lets look at site level mortality in sustainably harvested ducks relative to national/flyway mortality rates - Its not mega easy but as there is investment in such research in the US - we stay there /26

In Yetter et al - we find a treasure trove of info to help overcome simple but very dangerous assumptions in calculating harvest rates - from understanding duck daily movements to seasonal range sizes - but also the within site hunting mortality - in this case 30% /27

13.1M ducks were harvested in 2009 in NAmer, 14.7M in 2010 - for Mallards that was 4.1M in both years, Breeders were 7.7-8.5M - productivity at this time was 1.25-1.53 immatures per adult (= pop growth) - this is in the ball park of 30-40% harvest of Mallards in this period /28

This 2008-2009 harvest was too high - restrictions on bag came in after - but rates up to 20-30% seem to be sustained across the NAmer continent while site based mortalities at smaller scales can be similar - 25-30% - one has to question complaints about 1 or 3 or 6% /29

What is frustrating - is while the data are now robust - we have known about wild duck demographics, high productivity, high mortality up to 40% (Hunting+Natural) per annum, life cycles and migration for decades - so regulators are either out of their depth or bias is afoot ENDS

Thread has ended - but its important to be clear - it is beyond time we regulated wild harvest of waterfowl and game in the UK - its not difficult - it can happen - but it cant be applied to one group and not another - if @NaturalEngland want to get this running - lets talk

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